Movements and gestures

зажимать/зажать ноздриa to pinch one's nose
NB The above expression describes an action performed so as not to smell something unpleasant.
зажимать/зажать одну ноздрюa to pinch one nostril
NB The above expression usually describes what one does to close one nostril while leaving the other free to snort tobacco or narcotics, use a nasal spray, clear one nasal passage, etc.
вздрагивать [no Pf.]: ноздриn вздрагивают;
трепетать [no Pf.]: ноздриn трепещут
someone's nostrils quiver
раздуваться [no Pf.]: ноздриn раздуваются someone's nostrils flare
NB When applied to humans, the above expression usually describes a symptom of anger.