Mostly just piling on here...

I had issues last year and the only way to cure initially was take about a month off. Then do a month of stretching/strengthening. I did a lot of the following:

1. Arm straight in front of shoulder, bend wrist 90 degree up and rotate arm both directions, then bend wrist down 90 degrees and repeat. The key is getting a good stretch in the forearm muscles that extend into the elbow area and upper arm.

2. Hang from a pull up bar as long as you can

Then gradually ease back into hitting balls, but be cautious and error on the side of stopping if it's not feeling right. It may take a little time but you'll eventually build back up.