What Causes Pain In The Forearm Near The Joint?

Four days ago I woke up to a pain in my left forearm near my joint. Now my hand and forearm seem to be swollen. My veins are protruding in my hand and wrist. Earlier in the a.m. I could barely use my hand. I can't see any bite marks and took a benadryl last night . I'm thinking about taking ibuprofen tonight as the one tablet of benadryl didn't seem to make much of a difference. What could be the cause of this? It gradually has gotten worse. I'm 45, 5'2" 140 lbs, high cholesterol, low blood pressure, no heart risk factors such as smoking, drinking, etc., etc.