A baby’s sore nipples from breastfeeding may be due to improper posture, nipple eczema, mastitis and other related issues. 1. Improper posture: when breastfeeding the baby did not completely contain the areola and nipple, but part of the nipple in the mouth, sucking is very easy to lead to nipple pain. 2. Nipple eczema: after breastfeeding without timely cleaning of the breasts, resulting in nipple moisture, skin, eczema, accompanied by itching and pain, there will be a baby in the sucking nipple is very painful, you should immediately stop breastfeeding. 3. Mastitis: prolonged accumulation of milk in the mammary glands will produce mastitis in the breasts, and if the bacteria invade, pus will be produced, and it is necessary to evacuate the milk for anti-infection treatment. If the baby’s nipples are painful and accompanied by other uncomfortable symptoms, it is recommended to consult a doctor in time and choose the appropriate treatment under the guidance of the doctor.