Does naegleria fowleri cause infection if it gets into your nostrils or does it need to go deep into the nasal cavity?

Deep in nose: Naegleria fowleri is a free living amoeba that is present in freshwater bodies. People swimming in such water are at risk (a very low risk) of having the organism penetrate the cribiform plate (a very thin bone in the very back of the nose thru which olfactory nerves (nerves for smell) penetrate). Very rarely Naegleria are forced thru this plate producing an almost uniformly fatal meningitis.