Doubt about dark brown cuticle on fully bitten nail

Patient: Hello, so I’ve had a nail biting problem ever since I was very young. About 5 to 6 years ago, I remember biting my middle finger nail completely and never letting it grow to the point where the nail bed darkened and my cuticle is visible with a dark brown color to it. I ignored this until now, and I am doubtful about what it may be. I continued to bite for all these years. The nailbed is also darkened with 2 to 3 very thin dark lines passing along it. I am doubtful that this may be a Subungual Melanoma, but again I’ve had this for 5 to 6 years with no otherwise doubtful symptoms. This is only present on my middle finger nail.

Symptoms: None

Doctor: