The 26-year-old has been out since October after suffering a torn anterior cruciate knee ligament but came off the bench to at Hull to score a last-minute penalty.
"It's been a long eight months for me," he told the BBC. "I've been out for so long and it's just great to cap the end of the season off with a goal.
"To be honest I didn't know if we had a designated penalty taker; we usually have Peter Whittingham, obviously he wasn't on the pitch. A few of the lads were saying: 'Let Nicky take it,' and I'm not one to turn a penalty away.
"It was disappointing to get injured after two and a half games and with such a big injury, so just to be back on the pitch was massive for me.
"The lads have been so good, the manager Malky Mackay has been brilliant, the staff have been brilliant and it just shows how tight-knit we are."