The socket is the hole in the bone where the tooth has been removed. After a tooth is extracted, a blood clot forms in the socket to protect the bone and nerves underneath. Sometimes that clot can become dislodged or dissolve a couple of days after the extraction. That leaves the bone and nerve exposed to air, food, fluid and anything else that enters the mouth. This can lead to infection and result in throbbing pain that may last several days. Dry socket may start a few days after the extraction.