Tightness in upper chest left side towards armpit. Ekg normal, xray shows bursitis, MRI shows cyst inside bone, ortho. Says no problem. What now?

Need More Exam. Although your ekg was normal you may still have heart problems. You should consult a cardiologist. I doubt this is your problem though. A better physical exam and history may lead to other causes such as myofascial pain or trigger points. Trigger points are extremely common and my be the cause.
Pain Assessment. A cardiologist would be the most appropriate specialist to rule out conditions affecting the heart which can cause chest and left armpit pain.
See an Internist. You have many findings but no one has made sense of your symps. Orthopedics seem to think that the bursitis (presumably in left shoulder) isn't the cause of chest tightness. An Internist is your best bet to help figure out the cause. Lung tests or other procedures may be in order, depending on your history & family's. Or use HealthTap Prime to discuss your symptoms if you can't wait or find one. GL.