What is your diagnosis?
This is most likely epidermal inclusion cyst or Epidermoid cyst of bone
This is a bone cyst associated with trauma, especially penetrating trauma. It is usually seen in bones that are superficially located such as fingers, foot and calvarium. It is due to implantation of epithelium that form cysts leading to bone erosion. Subungual crush-type injuries (as in this case) have been associated with inclusion cysts as has prior surgery.
Contributed by Dr Tang