When there is a small hard lump on the left side after circumcision, it may be related to inflammatory stimulation, scar healing, foreign body reaction and other factors. 1. Inflammatory stimulation: circumcision is an invasive operation, and the circumcision area is very susceptible to contamination. When the wound is infected by pathogens, triggering a local inflammatory reaction, it can stimulate the local tissues, resulting in redness, swelling and itching and other symptoms, which can appear on the left side of the small hard lump-like manifestations. 2. Scar healing: scarring can occur when the wound heals after circumcision, local fibroblasts are active in proliferation, scar tissue can be formed on the left side, and small hard lumps appear. 3. Foreign body reaction: the tissue at the wound to the suture line, circumciser ligature line and other rejection reaction, can appear in the local small hard lump-like bump. After circumcision there is a small hard lump on the left side, should be timely medical treatment, clear cause of the active treatment under the guidance of specialists, to help early relief of discomfort.