Dermatofibroma: A common, benign skin growth that often appears as a firm, raised nodule, typically following minor injury, which matches the description given.

Molluscum Contagiosum: A viral skin infection causing small, pearly, or flesh-colored bumps, which can sometimes appear as firm, raised nodules.
Keratoacanthoma: A low-grade, or sometimes considered benign, skin tumor that can present as a firm, round nodule, often with a central crater.
Seborrheic Keratosis: A benign skin growth that can appear as a firm, raised nodule, although they are more often pigmented and have a stuck-on appearance.

Basal Cell Carcinoma: The most common form of skin cancer, which can initially present as a small, firm, raised nodule. Early detection is crucial for effective treatment.
Squamous Cell Carcinoma: Another form of skin cancer that can appear as a firm nodule, often in sun-exposed areas. It has a higher potential for metastasis than basal cell carcinoma.
Melanoma: The most dangerous form of skin cancer, which can present as a new or changing mole. Although less common, it's critical to consider due to its high mortality rate if not caught early.

Metastatic Skin Nodule: Rarely, cancers from other parts of the body can metastasize to the skin, presenting as firm nodules.
Leukemia Cutis: Involvement of the skin by leukemia cells, which can cause firm nodules among other skin manifestations.
Sarcoidosis: A condition that can cause small, firm nodules on the skin, among other systemic symptoms, due to the formation of granulomas in various organs.