ok so heres the problem...

whilst watching my fish i see a white cloud zip past one with an unusually

large bump on its head (just above its mouth and drooping down over it)

i thought it was just nothing but everyday it seemed to get bigger and now even preventing him from eating properly

so what is this? how do i get rid of it? can i get rid of it?

Is there any redness at all around/near this bump? Sometimes fish do suffer from tumors and such .Most times they're growths that don't kill them,but in a case such as this,when it's keeping him from eating,you may want to consider putting him down.
Before that last resort,the only other thing I can say is to try an Antibiotic.If its something that got into his system and went bacterial on him,then the lump may disappear with the help of meds and perfect params.
Any possible way to post a pic?