I tripped over something in the yard and fell, extending my right arm instinctively to break the fall. Later I noticed that the muscles in my upper arm were aching. Also, when I first wake up and move the arm, the upper arm and shoulder are somewhat stiff and hurt pretty badly. I watch TV in my room while lying on the bed, partially propped up by pillows. After about 15 or 20 minutes of this, my upper arm starts hurting, regular as clockwork.

What is particularly troubling about this is that the accident occurred 3 or 4 weeks ago, and there is no sign of improvement. Any ideas as to what this may be and, if so, what I can do about it?