You should take him to a vet, I had a problem with one of my other lizards that I had just gotten from a distributor, I thought it was excess shed, but it started coming off and there were scales missing. Come to find out, it was 2nd degree burns. The vet put something on it and she has healed nicely, she is even re-growing her scales instead of scarring.

My point is, you need to know exactly what it is before you can fix the problem, a trip to the vet is what I recommend.