Hi, while I was running on the treadmill before a workout at the gym today, I felt a strong pain near the center of my chest, slightly on the right side. Felt like it was my heart or lung or something. It was very localized, and did not shoot or radiate. The pain persisted for a few minutes after I finished running (it was a pretty intense run), then slowly subsided and disappeared as I lifted weights (less cardio intensive). Any idea what that might be?