It'll most likely heal itself. Any pain? It could be some bone chips from the extraction which are being "pushed" out by the gums. They'll come out on their own and the area will continue to heal. If you want to, the dentist can numb the area and remove the bone chips but if they don't bother you, I'd let it just heal on its own.
A related discussion, Bone on the floor of teath was started.