Help! What is on my fish's head?

[ThatFishChick]

So I just found this thing on top of my Banded Logsucker Marvin's head. Is this a fungus? Parasite? Or something I shouldn't be worried about? My nitrites are a little high. . .

 

[Delapool]

Pretty hard for me to see on phone. How long has it been there? Is it growing from inside out, or sitting on top. Possibly a tumour?

http://badmanstropicalfish.com/fish_palace/tropicalfish_disease_identification_1.html#Lymphocystis