To get rid of a sinus infection naturally try taking a hot steamy shower or sit in the bathroom with the shower on as hot as you can get it and let the bathroom steam up while sitting in the bathroom.
Steam is a good way to clear up sinus infections naturally.
You can also use a neti pot to wash your nose out with a saline solution.
If you enjoy spicy foods or can stand eating jalapeno peppers on some food then the hot spicy foods or even jalapeno peppers can usually open up your sinuses really quick.