Derm Dx: Pain at the base of a fingernail

The patient is a 52-year-old woman who complains of pain at the base of a fingernail. The condition was first noted 3 days ago and initially drained pus. She admits to biting her cuticles and to having a similar condition approximately 1 year ago. Examination reveals swelling of the affected site, and light palpation elicits tenderness.