On my left hand, ring finger, on the right side of it I have a dark colored line on it about 1cm wide. The skin right next to it is hard and is sore most of the times, I talked to a dermatologist about it and they said it doesn't look like a fungus, so they told me to see a hand surgeon, but I thought I would ask first here. When my nail grows it grows with it, sometimes it gets lighter and other times darker. I also had this on my big toe nail, but it went away and I had it on my middle finger on my right hand and it faded away also. The closest I came to finding out what it is, was deficiency in iron or something to do with melanoma, but the pictures they provided for that disease looked different than mine. Any information on this would be helpful thank you.