For some reason, I seem to never have any adverse reactions to touching corals that sting, or touching bristle worms. I always used to reach into my tank and smoosh them with my fingers (little did I know that the bits and pieces would reproduce). Now that I'm more edumacated a la Homer Simpson, I would still probably reach in and smoosh it to make more bristle worms! Anyways, on to the point. I would just pick your rock up off the substrate (I'm assuming it's on the bottom, but it may not be) because you've placed it where the bristleworms live. By moving it up, they're less likely to have a polyp snack cake, and leave it alone. If you have a concern about them climbing up and munching on corals, then buy a banded coral shrimp, or a hawkfish, and then when they leave the safety of the sand to adventure on the live rock in a quest for corals, they'll get eaten. The only thing I have on the bottom is a few mushrooms that fell down, and some xenia that are being culled and attached to rock for trading for the most part, and I have a banded coral shrimp which roams the tank during the night looking for wanderers. I started doing this after seeing a couple of leather corals I had become worm food when I buried their stalks in the substrate.