Hi. I have a thin black line on 3 of my fingernails on my right hand. Should I be worried?

Longitudinal . Melanonychia is something to take seriously. It is the increase of melanocytes in the nailbed. This can be related to pregnancy or hormones or sometimes prescription medications. Darker skin people are more likely to have these lines. You should have this examined especially if the lines have changed as they can be a precursor to melanoma in rare cases. .