I live in south texas. my son ran into a lake and got full of dirty water and had mud in nose. i'm scared he got naegleria fowleri. it's been 5 days.

Unlikely : If he's looking we and acting normal I think he will be fine as this is pretty rare. If he starts to become ill, has fever and chills or any other concerning symptoms see a doctor.

IT is VERY rare.: N. fowleri infection causes primary amebic meningoencephalitis which destroys brain tissue. Sx's usually begin within 2 to 15 days of exposure & may include sudden fever, severe headache, neck stiffness, nausea / vomiting, light sensitivity, feeling tired, confusion, loss of balance, hallucinations, seizures & death. If he appears well - then he is likely well.