nikon - Why is sharpness lost in my DSLR viewfinder?

I have a fairly new Nikon D7000 (I've taken about 2000 pictures).

Something happened during my last trip, where thew viewfinder never gets sharp anymore. It always looks out of focus, regardless if i am in manual or automatic mode.

Pictures still come out sharp, and when I switch to the LCD screen I can see the focus, but not in the viewfinder.

Is there some sort of tuning that needs to be done?

Answer

You certainly knocked the diopter adjustement out of place. It is there to compensate for people who need eye-glasses.

With your eye looking through the viewfinder, adjust the knob on the upper right side until you see what is in focus clearly sharp.