What causes a sharp stabbing pain between breasts closer to left side?intermittent.only lasts seconds.pcp says heart ok. should i seek cardiologist?

Trust PCP: The type of pain that you describe is not characteristic of either cardiac discomfort or any abnormality of the lungs or the large blood vessels of the chest. It is rare to actually find a specific cause, but if your doctor has done an evaluation and found no indication of a heart problem, there would be little to gain in seeing a cardiologist. In my experience this generally resolves on its own

Atypical chest pain: The description of your pain does not appear to be of cardiac origin.Cardiac pain usually lasts few minutes, is associated with shortness of breath,sweating, feeling of weakness ,is more like a feeling of chest tightness or heaviness & usually comes with exertion .If you are very concerned about it then only get a regular stress test to reassure you Dr Vishnu Gaiha