Sounds like medial epicondylitis to me (tendonitis of the forearm flexors).
Your GP will likely say rest it, or will offer a hydrocortisone shot to calm it down. The first is necessary, the second will weaken your tendons and ligaments in the long run (leaving you more susceptible to experiencing it again in the future).
I'd suggest PMing Ben Fury on this board for his AIS advice. I've personally found Low Intensity Laser Therapy (aka "cold" laser) to put out tendonitis "fires" very quickly (like 1-2 treatments). You can find practitioners near you (hopefully) with the same equipment I use at www.meditech-bioflex.com
Stop doing anything that hurts the area. This may be a lot of things. Work on your weaknesses that do not aggravate this problem. I'd suggest you go to low-rep weighted pull-ups (if any) for the time being. SDLHPs are an exercise that I consider to be well-covered by rowing and other pulls from the floor (ie. sumo DLs).
Cleans, thrusters, FS all irritate the area due to stretching the inflamed area under load. Pull-ups and SDLHPs irritate it due to the repetitive grip stress (forearm flexors do the gripping).
You better take care of this now.
Contrast hydrotherapy is cheap and easy, Google it.