Is this thing on my oscars lip bad

[Slammin’ Aquascaping]

Also, does anybody know why it is going black at the very bottom.

Could be the oscar’s immune system reacting to whatever it has. Maybe it is curing and that is a bruise from where this guy got the disease from originally. You never know unless you do your research. Good luck

 

[Big Boy Fish]

Update:
Its been a while and its almost halved in size. Hes perfectly fine and i recon it will be gone in months to come. Thanks for everything