Its not unusual for a Pacman to bite. They bite to defend themselves if necissary and some are just down right mean. I can't say for certain that he will be ok

. I am no expert and have never had. One of my frogs get a prolapsed intestine, but have helped people on here treat them. I believe the instestine was damaged and once it went back inside ot didn't heal correctly which is causing his problem. I would try the warm honey bath I mentioned. Let him soak in the water honey solution for 10 to 15 minutes.
He truely needs a Vet to confirm that he will be fine and to really figure out what the problem is. What are you feeding him?