I started getting sharp pain on top left side of left breast under armpit. it comes and goes every 2hrs but very sore. any idea of what this may be?

Injury/cyst/stress: While often breast pain is cyclic and related to the menstrual cycle, what you describe is not. Sometimes a sharp pain is the result of an injury/contusion that you don't recall. Cysts and fibroadenomas (benign) can develop and grow, pressing on nerves. Stress may cause tension in nearby muscle groups.This can be watched for a week or so if there is no lump. Use heat/ibuprofen. If persists, to Doc

Need an exam: Without examining the area it's difficult to give precise advise. Is there a lump in the tender area? If it's in the breast it could be a cyst. If it's in the axilla it's likely an infection such as a boil or abscess. In order to make a diagnosis and treat the condition you would have to see a physician.