I fell and fractured my arm in 3 places. I got some pins and rods placed iny wrist area. I was doing PT and couldn't lift my arm up all the way. Dr ordered a MRI of my shoulder. I have a torn rotator cuff, surgery not advised. So I've had to learn to use my right arm for reaching. So my advise is to get an X-ray or an MRI to make sure that it's all that's going on.

A few years back I started playing tennis and really enjoyed it. However I nearly lost my rotary cuff.

Yes I've rotator cuff issues.
B4 Parkinson's I played tennis, pickleball, and ping pong.
Me thinks Parkinson's at it now.
I'm 67 and played alot of racquet sports. They are weak points now and Parkinson's is going after them.

Wow. That's not fun. Neither is training you non-dominant side to learn to "pick up the slack". That's where audio translating our words comes in handy I guess. But I had to teach my left hand how to use a mouse for my computer and I am very right-handed. I muddled through until the cognitive problems kept tripping me up. I couldn't remember how to do things to hang on to Thoughts? I would lose my train of thought mid-sentence what a train wreck!
But learn to get around it for the most part. I am retired now. I was diagnosed in 2012.
Yep working around it. Keep in touch

I injured my shoulder/rotator a few years ago doing a push up challenge. The pain led to me not using that arm as much and I developed a frozen shoulder. I ended up doing physical therapy to fix it. I started with about 6 months with a therapist and then another year or so doing the exercises on my own to get full pain-free range of motion.