It sounds like some old skin retained from his last shed. Usually a shed is preceeded by milky eyes...and then the eyes clear up and the whole snake will look darker for a couple of days before shedding.


It would be fine to leave those spots alone and wait for them to come off with his next shed.

EDIT to clarify -- when I say "usually preceeded by milky eyes"....I mean, it always is, but sometimes we miss that phase if we're not looking at the snake very single day.