An itchy nose is a silly superstition that means that someone is thinking about you. In other explanations, it means that one is going to get a surprise. These are the main meanings but these could be varied according to different folklores.
Nasal flaring is when the nostrils widen while a person is breathing. It is a sign that the person is having difficulty breathing. It is most commonly seen in children and infants; in those cases nasal flaring can indicate respiratory distress.