Here Is A Strange Slightly-raised Horizontal Line Inside The Cheeks

here is a strange slightly-raised horizontal line inside the cheeks of my mouth. I think it might be whitish but it's hard to tell as it's difficult to look at in the mirror. They aren't sore so they don't hurt me at all, but if I lick along the inner sides of my mouth I can feel them there - they feel kind of like scars but that's not what I think they are. If I stick my finger in and scratch/rub at them a little to see if they can come off a bit of white stuff comes off with them? They've been there for about a week now or at least that's as long as since I've noticed..Do you know what they