Suck it up. Take 2 advil, wash it down with some beer and keep throwing batting practice.
But maybe change the order of the beer and the batting practice.
I think it was about two weeks before Labor Day. Me and a couple of the baseball boys were throwing the hardball around. Might have torn it then. Labor Day weekend my dd got invited to try out on a travel team. They wanted me to warm her up, that's when I noticed it. It hasn't gotten any better.