See below. This is a problem that requires a face-to-face meeting with his doctor. In that meeting, his doctor will listen to him, perform a throrough examination and possibly order labs or other tests. Based on this information, he/she will be able to tell him what's wrong and what to do about it.
I have a sharp pain in the lower left of my back, right above my bottom, it comes and goes. What is it and how can I stop it?
Many things. Think pulled muscle, kidneys, bladder, bulging disc. Probably muscle strain. I would rest, try antiinflammatories, heat. If that doesn't work, try core strengthing or see a doctor for eval.
NSAIDS, ice, heat... Pain, stiffness, and inflammation can be relieved with over-the-counter medications like advil or aleve (naproxen). Follow directions on label. Ice for about 45 minutes will address inflammation and swelling, never apply ice to the skin, always over a towel or clothing. Follow this by heat for about 20 to 25 minutes to help soothe and relax tight muscles. Gentle range of motion and stretching exercises.