Unfortunately, that is all to common with HEAVY use of the computer.
In the early days, it was "Mac elbow" from overuse of the mouse.
I switched to a Logitech trackball, so I use my thumb, instead of my index finger.
But then I overuse my index and middle finger turning the ball.
I really should do as my doc told me, LAY OFF THE COMPUTER for a while, and let your muscles rest and recover.
Ice to bring down the swelling, then heat to relax the muscles.
BTW, the other reason I use a Logitech trackball is, it is symetric, so I can use my left hand.
It takes a LOT of practice/training to get the left hand working, but it really reduces the workload on the right hand.
In the office it was funny. When I reconfigure for left hand, if anyone tries to use my computer, they went nuts. They don't know how to use a left-hand trackball.