After a tooth has been extracted, there will be a depression, or socket, where the original tooth was and it is not something to worry about, it is a normal phenomenon. For a short period of time after the extraction, a blood clot will form in the socket, which will help to stop the bleeding of the extracted tooth and prevent infection. Therefore, it is not recommended to brush or rinse your mouth for 2-3 days after the tooth has been extracted, as brushing or rinsing your mouth vigorously may dislodge the newly formed blood clot and cause the extraction site to continue to bleed, and there may even be a risk of infection. Usually the cavity will slowly fill in on its own over a period of about 2-3 months.