: An abscess occasionally complicates mastitis. You do not have to stop breastfeeding, not even on the affected side. In the past, an abscess was almost always drained surgically. Now, more and more, repeated needle aspiration or drainage under radiographic control is done, and interferes less with breastfeeding. If you need surgery, the incision should be kept as far away as possible from the areola. Contact the clinic.
A lump which isn't going away:
If you have a lump that is not going away or getting smaller over more than a couple of weeks, you should be seen by a breastfeeding friendly physician or surgeon. You don’t have to stop breastfeeding to get a breast lump investigated (Ultrasound, mammogram, and even biopsy do not require you to stop breastfeeding even on the affected side). A breastfeeding friendly surgeon will not tell you that you must stop breastfeeding before s/he can do tests for a breast lump.