my reef invertebrates book says you will experience symptoms ranging from a mild itch to severe burning sensation. Try removing embedded bristles with duct tape (the author must be canadian! LONG LIVE RED GREEN!) or to use a liquid bandage, allow it to dry and peel it off, along with the bristles.
Doesnt say "seek immediate medical attention" like it does when referencing the diadema urchin, so I guess bristleworm attacks are only annoying and not too too serious
