The hard lumps on one side of a boy’s milk are mostly due to the development of the mammary glands caused by the influence of estrogen levels in the body. Male children in puberty development is generally 10 ~ 14 years old, by the body of estrogen secretion will appear breast pain accompanied by hard lumps and other phenomena, this is a normal physiological phenomenon, with the body of the secretion of androgen increase and gradually alleviate, if the symptoms continue for more than a year, it is recommended to go to the hospital in a timely manner to do the relevant examination. The hard lumps in the breasts of young boys, it is recommended not to worry too much about the consideration of puberty development, it is recommended to eat a reasonable diet, eat more high-protein food, more physical exercise. At the same time, hard lumps may also be pathological factors such as breast hyperplasia, breast cancer, chest wall diseases other than breast, etc., need to be carefully identified. Parents should pay attention to their children’s body changes, if there is any abnormality can take their children to the hospital as soon as possible to do the relevant examination, under the guidance of the doctor standardized treatment.