What does the mark look like specificially? big, small, swollen, round, blotchy...?
Also did you mean that she is refusing to eat or is eating?
I am not familar with the hole in head disease, so PaPeRo will have to help you will treatment suggestions for that, I am however familar with a wide range of more common ailments and can help you there.
Hope she starts getting better soon,
Fantails and Betas