tennis elbow is a form of tendonitis. It is also called lateral epicondylitis and little leaguer's elbow. It is an overuse injury and presents with lateral (outside) elbow pain at the bony knob and pain in the forearm at the same basic area. It causes pain with grip and twisting motions of the hand and wrist. Treating of lateral epicondylitis involves anti-inflammatory drugs (ibuprofen, naproxen, others), rest from the offending action, and commonly using a tennis elbow band/forearm strap/whatever you want to call it. The strap is used to reduce the torque of muscle contraction at the tendon insertion at the elbow, it is placed over the meaty part of the forearm. The inflammation in the tendon will go away IF one lets it. The ongoing problem with tendonitis is that people don't let themselves fully heal.
Occasionally people will have to have steroid injections to relieve the inflammation. This works but can cause weakening of the tendon itself which can lead to rupture.
The other problem with tendonitis is not that the body is forever damaged because a person had tendonitis, but the same activity that caused it in the first place can cause it again. If you can increase your strength/endurance you can somewhat prevent re-occurance. I would also have someone who knows what they are doing evaluate your mechanics for throwing and hitting. Sometimes we do little flicks of our wrists to increase speed and don't realize that that is what the problem is causing the elbow pain.
If you had a specific incident which precipitated the elbow pain, the other concern is that you could have torn something in the elbow.
JMO-Hope that helps.
