Hello there. Off the cuff, this small thin pigmented line does not look sinister. Your habit of biting nails may not be the most hygeinic of habits but is unlikely to have caused this single nail issue. Longitudinal melanonychia is a benign condition. However, do keep this nail under observation with a pic and consult a Dermatologist once in 6 months. An Online Consultation with CLEAR pics taken in similar conditions of lighting, distance, camera etc for uniformity is important to make an objective evaluation 🙏

Kindly consult us online so that we can get your detailed history and prescribe you accordingly

Do not worry it is longitudinal melanonychia . Because it is unifrom and homogenous without any secondary changes as per picture , nothing to worry. Please do observe the lesion and we need to keep it under observation. Please do show a dermatologist every 3 months

Sometimes this could be sign of nail cancer so get it consulted by us

Well it is a benign condition. Need not worry.

Detailed history and clear images are required for correct diagnosis and treatment. There may be multiple reasons.

No need to worry.specific treatment is available.it depends on severity of the disease . Complete medical history is required.. Pls do online consultation with Dermatologist for detailed prescription & guidance.