I don't think corals store their eggs like that (I'm not sure if cespitularia reproduces with eggs anyway). As far as I know, corals release their eggs and sperm at the same time, and then the larvae become part of big plankton rafts and drift with the tides.
Those are probably going to hatch into something nasty that will feed on your coral(s). I'd probably put it into an isolated quarantine tank and keep a sharp eye on it, maybe post the pic in the diseases and parasites forum.