As an Osteopath I see fiddlers elbow , or tennis elbow, frequently.
As has been stated previously, it is a soft tissue inflammation, although whether muscle, tendon or tendon-sheath must be determined by inspection and tests.
Suggest strapping around the upper forearm, sufficient to restrict the flexion of the elbow, and GENTLE exercise. If it hurts after 30 minutes playing, reduce your playing time to 20 minutes.
Homoeopathic remedies Arnica sa an anti-inflammatory and Rhus Tox wil help the healing quickly, but must be taken in accordance with the manufacturers instructions.
If you are going to Chippenham Festival I will be there on duty asa Festival Osteopath.
Otherwise PM me if you want more information.
Colyn.