Its most likely bacterial. Those same infectiions we often see here on the forum and described as zits or pimples... They can be pretty serious depending on the bacteria involved. Its basically an abscess when it gets like this. The white "worm like thing" is just some forced out puss. Most of the time these pimples never get really bad as they rupture leave a small hole that closes up.. The above pics are what can happen if they don't and an an abscess forms.
Theres been a few times where people have reported these things happening to multiple fish at once and best we can do is guess theres a particularly virulent bacteria established.
I would seriously suggest a heavy duty antibiotic... Kanamycin, minocycline, oxytracycline are all good guesses.. If the member doesn't have access to them, then they should talk to a vet about whats available....a culture of that pimple may give a solid answer on the best med.
hth,
al