Yes, it is completely possible that he is fine. Chams do fall out of trees in the wild and they have several adaptations in their favor. Their ribs are cartilege not bone so they flex. When a cham feels itself falling it can inflate itself with air to help slow and cushion its fall. If you don't see any dark greyish areas on the skin (that's the sign of bruising in a cham) and no swelling on a leg or tail, he's probably fine. Bruises should heal on their own.