Is it a scar, damage, or is he just shedding? Discoloration on the face and jaw area can be caused by face rubbing in a too-small cage. The darkness can be a sign of an underlying infection. If it is real light and flaky he is probably just shedding. Maybe if you post some pics we can help you better? In any case, it is a good idea to bring all new animals to a herp vet for a check up.