How to fix a Nikon d3100 card reader?

I think my camera is messed up because my friend sat on it last night. Smh. But any way…

It says "This memory card can't be used. Card may be damaged. Try another one" when I turn it on and there's no card inside. When I try to put my card in, it goes in but doesn't "click" in. My card is in perfect condition. I put it in my computer and nothings wrong with it. It seems my camera thinks there's a faulty SD card inside when there's none.

I'm trying to see how I can fix this myself or if there are any CHEAP AND REASONABLE stores that can fix ONLY MY SD CARD READER for a good price. Anybody?

When Nikon repair gives you the estimate, bill your friend.