Hi, I am a healthy 34 year old woman, 54 125lbs.  I have discomfort on left side only of my chest that goes into my left collarbone and into my back.  It is slightly tendor to the touch.  I also have a cough.  Very nervous that something is wrong as this is the second time this year this has happened.  First time I was told was muscular.
Thanks for your question on Chat Doctor. I can understand your concern. Since you are having tenderness (pain on touching), musculoskeletal pain is more likely in your case. But better to rule out heart diseases first because of the left sided chest pain. So get done ECG, 2d echo and stress test (trade mill test). If all these are normal then no need to worry about heart diseases. Apply warm water pad on affected areas. Avoid heavyweight lifting and strenuous exercise. Wear rib belt. Take painkiller and muscle relaxant Chat Doctor.  Don't worry, you will be alright. Hope I have solved your query. I will be happy to help you further. Wish you good health. Thanks.