Need help to cure red lump on Clown Knife

[SNRMADE]

Gday guys
This is my first post and I'm after a bit of help on how to get rid of this red lump under my Clown Knife's jaw (see pics) I am currently treating him with Melafix and have done so for the last 5 days and NO change. He is in a quarantine tank and still eating. ANY ADVISE ON WHAT IT COULD BE AND HOW TO FIX IT.
Thanks

 

[guppy]

Is that lump solid or hollow and fluid filled. If it is solid then it looks like an injury where tissue was torn loose. If that is the case then as long as it does not get infected the swelling should slowly get better leaving a small tab of scar tissue, if it is hollow and fluid filled it may be furunculosis and should be treated with either furazolidone or tri-sulfa.

 

[SNRMADE]

gday,thanx 4 the advice guppy.i just put my hand i the tank and had a feel of the lump and it didnt feel overly hard,but similar to a hardish jelly feel.on the tip of the lump it has a clear,white kind of very small bubble.do u recommend that i should continue treating with melafix and maybe add some salt(not sure how much though) or try furazolidone or tri sulfa? your help is much appreciated.