Chameleons are lazy and as long as he is getting enough to eat by force feeding he probably won't bother to eat on his own. You will eventually need to wean him off of feedings to get him hungry enough to feed himself. You have a tough call to make as to how long to skip feedings because he is injured and still growing. I would start by skipping occasional days and maybe skip two now and then and see if he goes for a bug. Make sure the bugs you start with are very small he is going to have a hard time chewing without an intact lip. If you feed bsfl or wax worms puncture them with a pin so they get digested as he may not puncture them well himself at this point.
If you are feeding him Carnivore Care or some other enriched formula I would switch to an insect based formula with no added supplements and just add a touch of plain calcium yourself 6 days out of 7. Use the enriched formula no more than once a week. He will end up getting too much of the multivitamins and it could be stunting his growth. I use a plain cricket powder for body builders available on line.