Poor little guy! It's a good thing he's in the care of someone who will look after him.

That looks pretty nasty, although it doesn't look infected to me...Take him to a herp vet straightaway, see if they can recommend a good antibacterial, and have them check for internal damage. Just because it looks as though it's healing on the outside doesnt mean there's not a good bit of damage and infection to his insides. Make sure you keep him on superclean substrate, like paper towels only.

I agree that it does look like a burn, almost like he got in contact with a heating element. That looks like a big chunk of flesh he's missing, too...