Sore on my fish's head

[mike2lane]

There is this area on my fish's head that started with the skin looking raw and is now becoming worse by the hour. I have been doing this a long time, and I have never seen something quite like this. I would say it looks like a cold sore. It has progressed in this fashion for 4-5 days so far. She is still eating and swimming around like normal.

What do you guys (and gals) recommend?

NH4=0
NO3=40
NO2=0
pH=8.3
Alk=8dkh
PO4=.1
Ca=390

Thanks.