Hart appeared to be struggling with a back injury towards the end of the 2-1 win.
Platt said: "I think Joe's back spasmed as he kicked a ball.
"He is a bit blocked up and will be a bit sore tomorrow but he will be OK 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."