if you have a dremmel or a bandsaw you can cut it but only when the coral actually starts growing back , i.e when its healthy, Im also not familiar with the shape of the skeleton , if its anything like the button coral i wouldn't worry about it , since the skeleton inside is usually round, but if the skeleton has spikes on it like scollymia*, then you should cut it because the new growth usually ends up being cut on the spikes. Otherwise the current skeleton is no longer an issue this coral will make absolutely new skeleton structure without any regard to its dead part.