I'm looking for advice from people who have experienced similar nail problems. I know Reddit can't diagnose me, but I'd appreciate hearing about similar experiences and what kind of specialist I should see.
Context
I've had unusual dark pigmentation on my toenails, particularly my right big toenail and right middle toenail. The dark pigmentation appeared before the nail started lifting, and I noticed it changing and seemingly widening over time. I play some sports and have also used running shoes that were becoming worn out, with the sole deteriorating and part of the front sole coming loose. I'm wondering whether repeated pressure or trauma could explain the changes.
Also, the black toenail has been happening for about 2-2.5 months. Just in the last month, the black toenail started to become a bit worse with the nail lifting off the nail bed
What has happened to my right big toenail:
The nail developed a dark black/gray area that appeared to grow or change over time. At one point, part of the dark area seemed to be clearing in the middle. A white area appeared, which I believe was caused by the nail lifting away from the nail bed. The nail has become brittle, rough, and crumbly, with what looks like debris underneath. The nail is now almost completely detached, with the remaining attachment near the cuticle/base. There is dark, black-looking material (in spots) underneath the lifted nail. I initially thought there might be red material too, but I was mistaken; I don't see red material.
I went to a dermatologist (~ 1.5 months ago) inquiring about my middle toenail band. The dermatologist told me that a biopsy might be better but was about 95% sure it wasn't melanoma. They thought the pigmentation might be a hemorrhage, although they weren't certain. They also mentioned that the width of the dark area and its growth were concerning enough to consider further evaluation. The dermatologist only saw my middle toe black band, not my thumb toe.
What I'm wondering:
Could this be a fungal nail infection (onychomycosis), especially given the yellowing, brittleness, crumbling, and nail separation?
Could repeated sports-related trauma cause the black discoloration and eventually make the nail detach?
Has anyone experienced a nail that became black first and then gradually lifted off?
Does this pattern warrant a nail biopsy or evaluation by a dermatologist who specializes in nail disorders?
If you've had a similar experience, what testing helped distinguish fungus, trauma, and other causes?