Such a lump could result from an injury, infection, cyst or fibrocystic change. If you had previous breast injuries, fat cells in the breast tissue may be damaged and produce a firm, painful lump in the breast. If lumps are accompanied by breast tenderness and redness, it may suggest an infection. Similarly, breast cysts can also produce firm, tender lumps in the breast that change in size and seem to appear and disappear as your monthly hormone levels change. They often cause pain before your period is due and improve when the period starts.
You should get an examination, mammography and if need arises a FNAB done. FNAB is aspiration of the material of the lump which is done by a fine gauge needle (22 or 25 gauge) and a syringe.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.