A hard lump on the hand after being pierced by a glass shard may be caused by a localized foreign body, inflammatory reaction, scarring and other reasons. 1. Localized foreign body: If glass fragments are left in the wound, it may cause local bulging, which is manifested as a hard lump. 2. Inflammatory reaction: If the hand is pierced by glass fragments, the wound is infected by bacteria and other pathogens, which may cause local inflammatory reaction, local redness, swelling, pain and other symptoms, which may be manifested as hard bumps. 3. Keloid: During the recovery process after the hand is pierced by glass shards, connective fiber tissue proliferation can occur, forming keloid. It is recommended to go to the hospital in time after the hand is pierced by a glass shard with a hard lump, to clarify the cause of the disease, under the guidance of the doctor for standardized treatment. After the injury, tetanus antitoxin should be injected in time to prevent tetanus.