It can be done, but how hard it is depends on how much movement is in the shot.
If the actor is relatively still, you can use Photoshop to remove the blemish in a single frame, then import that frame into After Effects, and track just the section you touched up to your actor's movements. But you'll have to do this with each different angle...
If the actor is moving alot, it will be tougher to do it and make it look good. But then, if your actor is moving a lot, you probably won't see the blemsih that well anyway...