What is a hard lump in the chest needs to be considered from two aspects: one is residual milk, and the other is a hard lump produced by breast pathology. First of all, if you are a breastfeeding woman, if the child does not suck the milk clean when breastfeeding, the remaining milk will be blocked inside the mammary glands, and hard lumps will appear due to overfilling of the breasts and clogging of the mammary glands, and hard lumps inside the breasts are milk. Secondly, it is considered that the hard lumps are produced because of lesions inside the breast, which is considered to be breast hyperplasia, or normal breast tissue cannot be excluded. In addition, when a woman is developing, the endocrine hormone changes in the body will lead to the development of hard lumps in the chest, which is a normal phenomenon. Considering the complexity of hard lumps inside the breasts, if they are accompanied by tingling or tenderness, it is best to go to the breast department of the hospital for examination.