In 2017 I suffered a nasty fall. I landed on my right arm that was so in pain afterwards I was T-Rexin' that one arm for a few weeks. Too much flexion or extension hurt. Guess what set my arm right again: gym rehab. I was lifting weights then, and as soon as I was able I put the dinkiest weight on the bicep curl machine, 10 lbs or so, and just repped with that arm for a couple of sets. It hurt a bit, but training the arm got my body's repair mechanisms headed right to the site, and after a few sessions of this the arm became quite usable if not 100% pain free. It's pretty much back to normal now.