Possibly some stuck shed but it could be a skin infection of some sort. It's probably a good idea to bring him into an experienced reptile vet for a skin test to get a better idea of what that is and treat accordingly. In the mean time you could try putting some plain aloe on the areas and see if that helps it come loose. If the spot has been there for a year without spreading quickly it may not be anything more than stubborn shed. Best to have it tested to be sure though.