Collection of blood under the nail
There is a strong association with distal phalanx fractures.
In the past, complete nail removal and exploration and closure of possible nail bed lacerations was performed.  A prospective study of 52 children supports management with trephination alone for any size<unk> .
Atraumatic<unk>  may be caused by melanoma or Kaposi's sarcoma
The perinychium includes the nail, the nailbed, and the surrounding tissue.
The paronychia is the lateral nail folds
The hyponychium is the palmar surface skin distal to the nail.
The lunula is that white semi-moon shaped proximal portion of the nail.
The sterile matrix is deep to the nail, adheres to it and is distal to the lunule.
The germinal portion is proximal to the matrix and is responsible for nail growth.
Subungual hematoma
Distal interphalangeal dislocation 
Lip laceration
Distal phalanx 
Nailbed laceration
Finger amputation
Mandible fracture
Fingertip avulsion