There are two reasons for delayed menstruation and sore nipples: 1. When menstruation is imminent, the estrogen and progesterone in a woman’s body increase, causing nipple swelling and pain. 2. Pregnancy can also cause nipple swelling and pain. This is because both before and after pregnancy and menstruation, hormones are at a high level and will stimulate the nipples to appear swollen and painful. In this case, a blood HCG test can be performed to find out if the delay in menstruation and nipple swelling is caused by pregnancy. If it is caused by pregnancy, it is a normal physiological phenomenon and can be left alone. After pregnancy, you should take oral folic acid to prevent fetal neural tube abnormalities and have regular pregnancy checkups.