Well I just got my bottom set of braces off a few weeks ago and I got a lower retainer. The right moler tooth mold was alittle tight on my my gun and it cut my gum up. I went back to the orthadontist and he shaved alittle bit of the plastic off with a spinning file type of thing. I put my retainer back in my mouth about an hour later after lunch. The part that was shaved off is exremly rough and I cant do much to fix it. I guese the file thing left a grain that is anoying the side of my tongue terribly. Does anyone have any ideas to make this grainy feeling smoother.

I think you must consult your dentist regarding this. As they have such equipments that can help you out. You need not to do anything in this. This sandy feeling is common and it happens to everyone who gone through such procedure.