You sure it is a wart? Perhaps it is HPV that somehow traveled to your anus? Not sure or it could be just a regular wart. I've only gotten warts on my fingers and I believe once on a toe before.
Pus filled sounds like it could be an ingrown hair or maybe a pimple? Warts don't pop nor do they fill up with pus. You have to either dig and tear them out (which could cause more to spread) or freeze the shit out of them.
Search do ingrown hairs have pus and these are things that perhaps have pus
Razor bumps
Term for persistent irritation caused by shaving.
Boil
An inflamed pus-filled swelling on the skin, typically caused by the infection of a hair follicle
Cyst
In the body, a membranous sac or cavity of abnormal character containing fluid
Folliculitis
Inflammation of the hair follicles
Zit
A pimple on the skin
