Quoting ℳommy to Kai♥:" My four month old son just had his doctor's visit today. Everything looked great, although they want ... [snip!] ... just afraid what he did would have something to do with it. I guess I just don't remember if it's always been like this."
You never pull the foreskin back! D: I would have been so angry!
That probably injured it. :[
It may have tried to re-attach to the head and attached wrong. I would get him checked out by a professional and make sure the doc is against pulling it back! Poor baby.