I am so sorry you are going through this!
I don't know if I'm going to be exactly accurate here so don't quote me on anything.
It looks like there is a little bit of internal bleeding happening within the nail and I've heard and read that those cases could be due to liver problems, hemoraging (don't know how to spell it), or blood clotting issues.
I suggest make an appointment with your avian vet asap to rule out anything even if it goes away.
Don't mean to be that person to mention the scariest things but it really should be looked at!
Hopefully he feels better!!! So you won't have to worry anymore