My hamster has something stuck on it?

I can't tell if it's a scab or if it's food or if it's poop (which might be unlikely since her pellets are really small and whatever stuck to it is fairly large) it's been there for over a week and doesn't seem to be causing any problems but it looks kinda gross. it's about half the size of her head. i can't imagine it to be a scab since most she ever does is sleep. what should i do if it's something stuck to it?