Error message won't go away on Nikon DSLR?

I have a Nikon D3100, I took my memory card out a few days ago and when I went to turn my camera on today and it popped up an error message saying "This memory card can't be used-card may be damaged-insert another card" and when I tried to put my memory card in it won't stay in? Does my camera need to be repaired?

Just follow the error message. It isn't lying to you.

"when I tried to put my memory card in it won't stay in?"
That's a disturbing question, and probably one you'll want answered at a camera shop, where the staff can actually see what is going on.