I have no idea what a boring worm is. I have never heard the phrase before.
However if it is an external worm type critter then prazi is useless. Flubendazole in water may work and is possibly safer for cardinals. Cardinals are notoriously difficult to treat being intolerant of most meds.
If it were me I would remove ALL of the cardinals and humanely destroy them and watch the rest of the fish like a hawk.