Are you certain it’s a sinus infection or just allergies? I get sinus infections all the time when I’m sick and my allergies start acting up around this time of year. They sometimes mimic each other for me. There have been times where my sinus infection has gone away on it’s own, it just obviously takes a lot longer (took me three weeks i believe).
The reason I say this is because I caution you to take antibiotics for a sinus infection. Being on antibiotics and steroids for a sinus infection was got me here in the first place, so try and wait it out if you can.