Hard lumps on one side of the developing breasts may be caused by stimulation by related hormones. If the breasts are disc-shaped hard lumps may be normal, and if they are florid hard lumps may be abnormal. Breasts are in the stage of growth and development, breast cells may be stimulated by related hormones, pain or hard lumps may be normal. It is mostly normal to have hard lumps or swelling and pain if they are not chronic, or to have hard lumps that resemble discs. Hard lumps on one side of the chest, if they are petal-like, may be abnormal. Considering the possibility of localized lesions such as breast hyperplasia, breast fibroma, breast cancer, lipoma, etc., it is necessary to go to a regular hospital to do breast ultrasound to determine. If you are developing and have a hard lump on one side of your breast, we recommend you to go to the hospital in time, complete the relevant examinations, and take the appropriate treatment plan after clarifying the cause of the disease.