Australian Arowana Disease Please Help.

[Xscape]

I spot this few days ago, since then i do water change every 2 day and add salt.
Has anyone have the same problem before or any suggestion to cure it.
He still eat and very active.
(It look like a pimple)
View attachment 726133

 

[ausarow]

cant see it very well, the only thing ive ever seen sticking out that much on a fish
is something like a tumour.

 

[ausarow]

has it got white junk in it? or just raised red? i have seen fish with white pimples that squeeze out. the other one
is a solid tumour that never goes away unless its surgically removed.