I had tooth #14 extracted due to a cavity & dentist said my sinus was exposed. What does this mean? How long til heals completely? It’s been 4 days.

Oro-antral opening. This occurs when the roots of the maxillary teeth communicate with the maxillary sinus. When the tooth is removed, there is an opening between the sinus and your oral cavity. This usually heals on its own without incident. To help promote healing and to avoid repair surgery, do not blow your nose until the area is completely healed. Allow your dentist to monitor the site.