I live in a big town was careless and had small amount of tap water go in my nose and down my throat terrified of catching killer diseases plz help!!!

Unlikely: even contaminated water has low risk, but , the US cities tap water is quite safe. Your own nasal bacteria are swallowed regularly. Many other higher risks.

You need help: not for fairly safe small amount of tap water going down from throat from nose , for your germ phobia . We are all exposed constantly to germs , constantly battling with bad bugs .We have 10 times more germs on our body ( some even help us ) than genomes of our own body cells have to avoid only few . Speak to your doctor try to over come this fear . Good Luck