The hole in the middle of the nipple is called the milk hole, which is the opening of the milk ducts in the nipple and is designed to allow milk to flow out during lactation. If the hole in the middle of the nipple is large, consider the following possibilities: 1) The hole may be large because the patient’s breasts and nipples are large. 2) The hole may be caused by the fusion of two breast holes close together into one, resulting in an increase in the diameter of the hole. 3. It may be caused by inflammation of the nipple. The size of the milk hole does not affect the outflow of milk. If there is no inflammation, blood-like overflow, pain or other uncomfortable symptoms, it is considered normal, but if there is any abnormality, you should seek medical attention.