What Causes Soreness In Left Leg And Inner Elbow?

Thanks in advance. For about three weeks I wake with a soreness in my left arm near the crease of the inner elbow but above it and on the inner side toward my body. I notice a swelling which feels slightly rounded and to me that area looks different from my right arm when outstretched, palm up. I am a 64 y old female and have not had an injury there. I hate to run to the doctor about every little thing! There is no bruising and the soreness is never intense. I am more concerned about the appearance of swelling there. What might be causing this?