I have a sharp pain in the center of my lower back accompanied with a small indentation. Bending and standing up straight are painful. I work out regularly and noticed it was really hurting the other day while I was doing squats. Any idea what this could be?
This looks to me a back muscles spasm.  I would still recommend you to get x-ray of your spine.  If there is nothing wrong with the bone then take tablet moral or MySpace. Also take warm water shower on back. Avoid bending forward and lifting heavy weight.