Thanks for posting,
According to your description, I may assume that your pain is mild. It could be a neuralgia
(unknown origin) or might be an inflammation or maybe coming from your heart (possible coronary artery
You might need that your breast be examined more closely by a GP.
Given that the pain is very unspecific (not typical to any particular diseases), you will require a doctor to look through. You may take analgesia pain medication to try to relief you from the pain or antispasmodic.
hope this helps