The specific reasons for the hard lumps and pain in the breast of an 8-year-old girl are as follows: First, if the girl’s breast is traumatized, it will cause a local hematoma, which will cause a hard lump along with painful performance, so you need to ask if there is a history of trauma and observe whether there is local swelling. Second, if the child does not have a history of trauma, but has pain and hard lumps, he/she needs to go to the hospital for ultrasound examination to clarify whether it is mammary nucleus development, and if it is mammary nucleus development, then early sexual development is considered. If there is a loss of height, a detailed examination should be given under the guidance of a doctor for further treatment. If there is no loss of height for the time being, guidance on life, diet and exercise should be given according to the child’s current condition to intervene in the child’s sexual development.