If you'll look around the interwebs for shoulder mobility stuff, you should find lots of movements that will make a difference. I had shoulder issues from football as a teenager, but now, through addressing the issues and strengthening the muscles and tendons, my shoulders are good to go and stronger than ever.
Don't be afraid to bring up any and all issues you have, even if you aren't sure if it's a big deal. There's a ton of experience running around this forum, and we all want to help any way possible.
Current PRs at 242- 495, 345, 585, 1425