Steve, I’m definitely not a medic but always believed that tendonitis is also called tennis elbow. Not suggesting that you’ve been playing tennis (or maybe you have!) but think that something like ibuprofen should help cure it tho it may take a while. If you’re really concerned see your GP but don’t let it take away your normal positivity will you.
It’s not fair Steve , my left arm is painful and stiff and won’t bend like it should it’s awful when my back itches or when I need to undo a zip on my dress or even if Frazer poos in a walk I really struggle to pick up with a poo bag . He walks on the left of my chair so it’s always that arm. I hope you feel better soon. Michelle and Frazer xx