I wonder for those who have had this happen, ever get that pain again every once in a while? It starts in the shoulder, soreness, then moves to the lung - like a semi sharp pain when i take a good deep breath. It usually goes away in a few days. Lung collapsed 2x when i was 17 but not since (10 years). I would go get an xray if it persists for a few more days but since I know this feeling I am not getting too worried about it - mainly it's just annoying! It comes up maybe once a year...usually after a good exercise, maybe a race or hard workout.