I was doing a two hand cable preacher curl, finished my set and decided to do a rest pause. After resting three seconds with my shoulder blades protracted leaning forward over the bench I curled the weight up again. It was about my 8rm. I heard a snap and crackle in my left shoulder. When I placed the weight down I felt another crack in my shoulder and from then it has been feeling a little unstable with a dull ache. I can move it everywhere but it feels unstable and painful if I stretch my chest on the right side or place my elbow behind my body at all.
What can I do to fix it? Any rehab/prehab moves I should be working on and any idea what may have caused it?