Hard lumps from wounds covered by old skin may be due to keloid scarring, infection of subcutaneous tissue, or suture rejection. 1. Keloid scarring: some patients will have obvious scarring during wound healing. This proliferative scar tissue is hard to touch and can usually soften with time. 2. Subcutaneous tissue infection: After the wound heals, there may be subcutaneous tissue infection. When infection occurs, it can cause redness, pain, warmth and hardness of the affected area. If the infection is serious, the patient may also have fever. 3. Suture rejection: patients with large wounds need to be sutured, after the suture may cause local skin rejection, resulting in a hard situation under the wound. Patients should take good care of their wounds, and should seek timely medical treatment if they feel unwell during the recovery process.