I've had lower right arm pain for over a week now, at first I thought it must just be a strain, tennis elbow or similar but it's become so painful over the weekend. It's now swollen, my right arm is about 3cm wider than the left. The pain is like a constant dull ache. My skin feels tight too. If it was my leg i'd be concerned about a blood clot. The pain seems to be worse at night. Any suggestions as to what this may be? Thanks