Subungal haematoma
A subungal haematoma is usually caused by a blow to the toe which may, or may not, also cause a fracture. The pressure from it often causes pain and this can be significantly relieved by trephining the nail to allow the release of blood. However there is no evidence to say that this treatment is better than no treatment [4].
It is sometimes argued that patients with an underlying fracture should be given antibiotics as the act of trephining converts a closed fracture to an open one. However antibiotics do not seem to be necessary [5].