There are several possibilities. 1, lipoma. In the superficial subcutaneous position, it is slightly painful, softer and harder than the surrounding normal subcutaneous adipose tissue, and its appearance is mostly slightly convex. This kind of tumor is usually very small, from peanuts to eggs. No problem, no treatment is needed. 2, muscle nodular inflammation. Large pieces (such as eggs) have obvious pain, hard and deep feel, inconspicuous edges, and generally hot appearance, but not obvious redness and swelling. Need to treat syndrome. 3. Acute infectious inflammation. The appearance is obviously red and swollen, and induration is painful. Need treatment. 4. Old injuries. Generally have a history of trauma. Only hard, or protruding, but not painful. Generally, no treatment is needed.