If you find a hard lump in your left breast with painful manifestations during breastfeeding, it is more likely to be an inflammatory lump. This is because during breastfeeding, especially in first-time mothers, it is easy for milk to accumulate and for inflammatory masses to form. Because milk is the best culture medium for bacteria, it is easy for bacteria to grow after stagnation, and the patient will experience local pain, which will be limited if the inflammation is treated promptly and effectively. If the inflammation continues to develop, the patient will also show fever and even increased pain in the breast, which can be treated with systemic anti-infection therapy along with physical therapy such as hot compresses. It is also important to keep the milk emptying smoothly and to pay attention to local hygiene to avoid aggravation of infection and to be alert to the occurrence of breast abscesses.