Well, if you are feeding live then it's possible the injury could have come from the claws of the mice feet. They are very sharp as are the teeth. So, it could be several causes but for sure it centers around the live mouse more than anything else. Just my .02 cents. Beautiful reptile btw. Feed f/t so he doesn't get scarred up. If e feedings he'll switch over. Good luck.Try to monitor those live feedings as much as possible to avoid accidents and injury to the bp in the future.