Upper arm healing process

[Kentannenbaum]

Trusted ortho surgeon gave me a cortisone shot for an arm injury lifting roof panels.  Said there's NO shoulder damage and the muscles are fine and that IF the cortisone doesn't last (it dissipated in a couple of days) if I wanted it, he get an MRI for me.  I'm 71 and in good shape but it bothers me some but I'm basically okay and can live with it.  Typically for me, injuries heal giving enough time.  My question is if there's lots of evidence that time and stretching could do the trick.  Thanks.