Nikon DSLR focus ring jammed?

A couple days ago my Nikon D40 was working perfectly, but the other day I noticed the focus ring would not rotate all the way as it should- You can feel the sudden stop. I can't focus on landscapes and moderately far away areas. When I say I have to be really close to focus, I have to be within an approximate 3 foot radius of my subject.

Are there any tips you can give me to fix it? It would be much easier than replacing it. Thank you.

Added (1). I have a 18-55 mm lens. I acquired the camera through a friend in perfect condition, but the D40 model is pretty old.

What lens is it, and how old is the lens?

Either way, there's nothing you can do to fix it. It would need to be handled by the manufacturer (and it may be under warranty). That is the reason I no longer buy Tamron glass, I have had various issues with zoom/focus rings sticking/slipping.

What lens? Some lenses have a MF/AF switch, some lenses have a "macro only" mode with another switch to keep the lens from "focus hunting" when shooting closeups.