30 Gallon Tank HELP black lump on goldfish

My Ryukin goldfish has recently gotten a black growth on her side. She has had a black spot there for a few months but it has recently become a lump. She is behaving normally and water quality is fine.
ammonia: 0.25 (i know, slightly high but i am doing a water change tomorrow)
nitrate: 5
nitrite: 0
I’ve done some research and have no idea what it could be. She is alone in a 30 gallon and I’ve had her for just over 6 months. I attached a few photos.

 

How is her behavior? Anything irregular? Have you found anything on the internet that seems to look familiar to it? Poor fish.

 

She is behaving completely normally. Very active, eating, coming up to the glass to see me, all the things she normally does. I've done some googling and seen nothing that looked similar at all. It's really strange, I've got no idea what it could possibly be.

 

A201 is the disease guru, maybe they can offer assistance. Good to know behavior is normal at least!

 

Looks like it might be "Black Smudge" it's a blacked tissue reaction to elevated ammonia.
The remedy of course is a constant level of zero ammonia.