Just slightly tore my rotator, not from paddling but Olympic overhead weightlifting so ... just hit the PT and rest/theraband deal.
If it continues to hurt I'd go to a SportsMed doc and get it xray and evaluated.
You can do Theraband shoulder/rotator PT excercies year round to keep the joint stable. They take a couple of minutes a few times a week and help a lot.
My wife (paddler) has very unstable shoulders and she has used regular theraband to keep the rotator strong and in shape when not paddling.
Sorry I do not have a link but they are pretty standard rotator excercises-- should be able to locate a url.
Good luck with it-