This happened about a year ago. Yes the entire toe nail is black.
Yes, it turned black on its own little by little until the whole toe turned black. Then my pinky toe and the toe next to it started getting very inchy so I put foot medicine on it and then it was better for a while but ichyness come back on the pinky toe and my Big toe continue to stay black.
I notice it is only on my right foot the other foot has not problem at all.