hi if you Google this exactly it gives you all the common and rare side effects of percocet. It's rare side effects of percocet and this should help you more, i didn't see anything on there that says gum bleeding this is usually a sign of gingivitis which could show up at anytime the only other thing i could think of that would cause his gums to bleed from percocets would be if he was chewing them up the acids might have irritated the gums but definitely get to a dentist and get him some over the counter mouth wash called proxel its in a blue box at walmart very good for the gums, i use to be a dental assistant that's how i know about gums and i am a percocet addict. i wish you too the best of luck.
Hi! I'd say a trip to the dentist is in order. Regardless of the cause, bleeding gums need to be looked at and treated. Beefing up on extra vitamin C will help,as well.
Good luck to him~