Doubt about water going in nose.

Hello Sir/Madam, my query is that how can the water get into the sinuses via nose. I mean if by chance while washing face/hair, a drop here and there falls in nostril, can it go into the sinus? Or if we accidentally breathe in, the water can go inside the sinus or one has to breathe in aggressively for water to go into sinus. Sorry, I only am asking because a drop of water fell in my nostril while pulling a towel above my head, that has made me paranoid with fear of N Fowleri infection. I mean the tap is used daily even if sparsely, but the tank of borewell connection is same that we use often have used for 9 years. Can taking Azithromycin now help ward of the infection? I will be grateful to a kind Doctor who can answer my query. Please don't write that I can contact you for a paid consultation if you can't answer my query. Thanking you and utmost regards.