Dark spots on fingernai

[Chrlne]

Hello, for the past 2 months I have has dark spots on one of my finger nails with a white patch over the top. It also have a light brown bruise colour underneath. I haven't injured myself, its not sore and not a fungal infection or deficiency/dietary according to my GP. I sae him a month ago and he told me to keep an eye on it and come back if it's not gone. It has moved with my nail as I've been documenting so I don't think it could be cancer, how we, about 5 months ago a had a biopsy on some swollen nodes on my neck which are still there. I've been reading that if it grows out with your nail then its not cancer, what other diseases can cause this?