Platt confirmed Hart suffered a back spasm attempting to make a clearance during the second half of City's 2-1 win over West Ham.
With all three substitutes used, manager Roberto Mancini did not have the option of taking Hart off. But the injury was clearly troubling the England man and caused the mistake that gifted Andy Carroll Hammers' injury-time consolation.
As City still have four Premier League games left, plus the FA Cup final against Wigan in a fortnight, any extended absence would be a concern.
However, Platt is adamant that is not the case.
"I think Joe's back spasmed as he kicked a ball," said Platt. "He is a bit blocked up and will be a bit sore tomorrow but he will be okay on Monday.
"It possibly affected him with the way he conceded the second. If you look at the ball when it has gone in he can't get down to it.
"Most keepers, because they are throwing themselves about left, right and centre during the week will have issues around things like that. It is not much of an issue. It is a 24-hour thing."