The Olympic bronze medal winner tore his triceps in April and suffered a recurrence of the injury during Thursday's warm-up.
The 19-year-old received treatment between each round during the first qualifying session and the semi-finals, finishing 13th and seventh respectively to reach Sunday's medal showdown.
He totalled 452.70 points in the semi-final, as the USA's David Boudia topped the session with 534.40.
has played down his medal hopes after only returning to training in the past month.
“Anything can happen but medals aren’t necessarily in the forefront of my mind," he admitted. “I’m through to the final, that’s the main thing but it’s been a bit of a rough day.
“I woke up with sore triceps and when you wake up on competition day with that it’s the worst thing that could happen, because there’s so much force which goes through them.
“I’ve had to work with the medical team who have been so good, they’ve been nursing me back together.
"At the moment it’s hard to get better when I’m still diving on it but anything can happen. It’s going to be a tough one and everyone’s diving so well.
"With this triceps injury and the preparation I’ve had after being injured all year, it’s just one of those competitions where I have to go into it and give it my best shot knowing it’s kind of a miracle to even compete."
Team-mate Daniel Goodfellow finished 28th in the first qualifying session, failing to reach the semis in his first major international event.
Germany's Thomas Lurz became the only man to have struck gold in all four open water events when he battled through the pain of the final sprint to edge the 25-km race.
The balding 33-year-old from Wuerzburg, who took silver in the 10-km race and bronze over 5-km earlier in the week as well as gold in the 5-km team event, slapped the overhead finish marker to register a time of four hours, 47 minutes and 27 seconds after a marathon slog around the city's picturesque harbour.
Brian Ryckeman of Belgium came home just four tenths of a second later to take silver in a time of 4:47:27.4 followed by Russia's Evegenii Drattcev in third with 4:47:28.1.
"These championships have been great for me," Lurz said.
"I was lucky to be in the middle (for the sprint) and I had a little bit of space.
"I closed my eyes for the last 100 metres, I was hurting, I had so much pain but I said, 'Now I give it my best'."
Lurz's compatriot Angela Maurer was unable to celebrate her 38th birthday with another gold for Germany after Italy's Martina Grimaldi edged her by a tenth of a second in the women's race following more than five hours in the water.
Maurer, who won 25-km bronze at the world championships held in Barcelona a decade ago, was devastated after initially being declared the winner, but said she was still pleased with silver.
Grimaldo came home in 5:07:19.7. Maurer, world champion in 2006 and 2009 and a silver medallist in Shanghai two years ago, followed in 5:07:19.8 and Eva Fabian took bronze for United States with a time of 5:07:20.4.
"I don't know what happened," a dripping Maurer, her eyes still showing the marks of her goggles, said.
"I just tried to touch and maybe I didn't touch strong enough," she added.
"It's a little bit frustrating if you see you are first and then you see you are second.
"I'm a little bit sad but I did a great race so second place is also fine. I got a medal and that was the important thing."
Lurz dominated the 5-km distance at previous world championships, winning seven straight golds between 2005 and 2011, but had never medalled in the 25-km version.
He won gold in the 10-km in 2004 and 2009 and is also the only athlete to have won an open water medal at two Olympic Games, taking silver in the 10-km swim in London last year and bronze in Beijing in 2008.
Russia underlined their total dominance in the synchronised swimming programme by completing a sweep of all seven gold medals with victory in the free combination team event.
After winning all seven titles at the previous world championships in Shanghai two years ago and six out of seven at both Montreal in 2007 and Rome in 2009, the 10-strong Russian team wowed spectators at the Palau Sant Jordi with a typically acrobatic routine to amass a points total of 97.060.
Spain got the home supporters rocking with a rousing Elvis Presley-themed routine to take silver with 94.620 and Ukraine clinched bronze ahead of Japan with 92.020.
"We did here our maximum," Svetlana Kolesnichenko, who teamed up with double solo gold medallist Svetlana Romashina to win both duet events, told reporters.
"We did everything that we wanted to do so it's a big mix of emotions."
Alba Cabello, at 27 one of the senior members of the Spanish team, said she and her team mates were now looking ahead to the next Olympics in Rio de Janeiro in 2016.
With China competing in Barcelona in the solo and duet events only, Spain held off the best of the rest to take three silvers behind the Russians in the team competition.
"If someone doubted that our team could win a medal in each event, they can look at the result and see that we've reached our target," Cabello said. "We will continue to fight for medals."
- Sports & Recreation
- Thomas Lurz