I Have A Tenderness In The Upper Left Side Of

I have a tenderness in the upper left side of my abdomen which hurts more when I am lying down or sitting up or lifting something. I recently fell backwards in my yard and hit the back of my head. I had pain afterwards in the neck muscles and noticed pain in the stomach muscles. This has gone but the pain in the stomach muscle remains. Could this be a result from the fall, and what can I do?