hi. it is best if you consult with a doctor, preferably a breast or a general surgeon, for clinical evaluation. based from your description, it could be mastitis or a breast inflammation secondary to breast feeding. it could also be due to a cyst, a fibroma or a fibroadenoma which are all benign breast lesions. other tumor lesions such as malignancy must also be ruled-out. diagnostics such as breast ultrasound and a possible tissue biopsy may also be recommended. management (medical and/or surgical) will be directed accordingly. hope this helps. good day!! ~dr.kaye