It's a little hard to tell since the pic is a little blurry. What do you feed him, f/t or live?
I would sterlize his enclosure ( remove all substrate, use paper towel or newspaper, remove everything from his enclosure other than the water bowl ) clean the wound gently with some betadine, make sure temps are perfect ( or atleast dang near ) up the humidity a bit and let him heal. If you notice any nasty oozing, bad smell or anything indicating an infection, please seek a vet ASAP.