Nikon D3100 trouble shooting, adjustment dial doesn't adjust?

I have been using my D3100 extensively since purchasing it in august 2011, one night a friend used it for 5 minutes to take pictures of my fiance and i, ever since then i have been unable to adjust any of the settings manually (while in ANY of the M, A, S, P settings) using the dial that sits directly across from the "AE-L AF-L" button.(which is the dial i have always used) I have tried trouble shooting this 100 ways, but to no avail… Please tell me what my friend did!

We can't tell what your friend did. Check your manual on how to reset the camera to factory settings.
That should work.