If so it would be some sort of ice volcano. I didn't find where it said what the spectrum was for the camera, infra-red? visible? something else? One theory for it is that it is a dust covered ice ball, a large enough impact could uncover the ice (although I would expect there to me a sublimation cloud at that point.)

If the core is nickle iron it could be a chunk that melted and reformed after impact.

Or it could be a bad pixel :-) but that seems unlikely as it moves with Ceres and not with Dawn.