Probably could be either one. I have had them erupt through my gums up to six years or more after the teeth in the area had been pulled. I grabbed them with a pair of tweezers and pulled them on through. Had one splinter that didn't work with and ended up going to the dentist who took a drill to it and attempted to smooth it enough the gum would grow over it again. (also didn't work) He had to refer me to an oral surgeon to get the entire bone shaved down.

I can feel for you. It is kind of scary when this happens. I understand it can be either one, tooth remnants or bone. I wonder what makes that happen??