How do I realignment viewfinder

I have had a D5100 for several years. A couple years ago I dropped it. Everything still works except that I can not get a sharp image in viewfinder. It is impossible to focus manually but if I set up my focus points where I want, the autofocus will do a fine job. Images are perfect. Live view also works and gives sharp image but that drains batteries too fast. I have determined that the prism is slightly jarred out of alignment causing the eyepiece to be out of focus. Not sure how or if this is fixable. What is your experience with this area? Thanks.