I had upper right second molar pulled do to infection 3weeks ago sinus infection ever sense socket still deep and open could it be do to tooth infecti?

Tooth\Sinus Infect: Infections can spread. A tooth infection can spread to sinus & this might have happened even prior to the extraction of the tooth. There is no way to know for sure. The sinus infections might have been brewing without your knowledge. What's important is that you receive the proper antibiotic coverage and have your dentist evaluate for oral-antral communication. Discuss also with ENT specialist\GP.

Oroantral fistula: also called oral-maxillary sinus fistula. They are usually encountered as complication of tooth extraction. A fistula can cause chronic inflammation or infection of the sinus and surgical intervention is warranted. Good luck.