Weird one. Is it defo a growth? Have you fed any worms lately only sometims mine can't fit it all in and a bit sticks out their mouths and it looks like that. Just a suggestion.
It appears to be a lip fibroma, most commonly found on angels & other cichlids. It's only a problem if it prevents the fish from eating, a solution can be found in my response here.
As long as they are kept in really clean water for about a week it isn't an issue. The problem with not removing it is that eventually the fish can no longer eat.