Muscle injury under left rib cage

I seem to have strained a muscle while playing golf a few days ago.  The pain was not too bad but noticable.  Then last night, a aggravated it while playing tennis.  The pain is now more severe.  It is on my side and goes around both my front and back side just under the rib cage.  It hurts most when I cough or tighten the area in any direction such as bending over or twisting.

Any ideas what this is and how I should treat it?  Thanks for any advice.

[sharittwo]

I have been dealing with left side pain in my back and in my ribs for 3 yrs.  I had a lot of trauma to  this area and the pain feels like my left side is being constantly stretched and my ribs feel like they are crushing.  The pain goes down into my hip area were that muscle is above the buttocks. My left leg and arm go numb and tingle.  When I sit all day it hurts and I can't even stand up.   I have been doing trigger point massages that really worked,  After I have been to every doctor and no help.  I also am going to a pain management doctor now.  I would try a trigger point massage.  Good luck.