Pain in side

Early last week when I reached forward on the cross-trainer a sharp pain came high on my side making me wonder if some shoulder-related muscle attaches to my rib there. Not wanting to aggravate it, I took some days off exercising and still felt that pain, albeit infrequently. Today I tried working out again and after a few minutes the pain returned. I relaxed that arm a little and continued on the cross-trainer and after a few more minutes I felt okay again. So, that worked out nicely: there does seem to be a strange issue there but perhaps not one that prevents my workout.