Not trying to argue but I just want to be clear, tennis elbow and golfer's elbow aren't the same thing. Tennis is lateral elbow pain while golf is medial. Using one treatment protocol for the other is actually contraindicated and can/will make the pain worse. Again, don't mean to be argumentative, I'm just anal like that.
To the OP, what do you do that causes pain? What's your daily activity like? Job like?
The suggestion of using a rubber band around your hands and expanding is a great remedy. You want to do this A LOT. And as mentioned, the size of the rubber band is important. A regular rubber band normally doesn't get the job done though. One of those grocery bands that they put around asparagus or whatever works much better.
Some manual therapy (ART is one form of this) is a great idea. Get this done on the medial portion of the elbow (where you have pain), but not the lateral! You can also simply do some massage work yourself on the medial elbow. Work in a vertical fashion more so than a horizontal one.
Lastly, stretch your wrist flexors and finger flexors (see picture). Do not simply pull your hand back but use a wall!
The reason for this, as you'll likely notice with using the wall, is your fingers will still be flexed when you're pulling the wrist back. That is, your palm is flat on the wall but your middle knuckles aren't.
So by using the wall you can see your fingers that are still flexed, now you simply extend them so your entire hand, including the fingers, are all flat against the wall. This way you know you're stretching the wrist flexors AND the finger flexors.
Hope this makes sense; keep us posted.