How we change what others think, feel, believe and do
Nose body language
The nose, which is right in the middle of the face, can send a certain amount of body language.
When the nostrils are widened it allows more air to be breathed in and out and readies the person for combat. In a related sense, this can indicate the person is experiencing extreme displeasure.
Flared nostrils may also indicate that the person is making an internal judgment about something.
The nose can be wrinkled by pushing up from the mouth, pushing the cheeks or pulling from the top. This happens when a bad smell is detected. It can also appear with a metaphoric bad smell is thought about, for example when somebody else suggests a distasteful idea (see: even language uses bad-taste metaphor!). Card players may do this, for example, when they are dealt a bad hand.
Another variation is when the person is thinking about something but is not satisfied with their own ideas.
Aside from when a person has a cold, sniffing can indicate displeasure or disgust. This may also happen on one side, with the mouth twitching up as well.
Touching the nose can indicate that the person has detected a bad smell. It is also common signal from a person who is not telling the truth.
When a person lies, blood vessels in their nose may dilate, making the nose swell or appear redder. The nasal engorgement then causes mast cells to release histamine, which makes the nose itch and so may lead to the person touching or scratching it (this is probably the basis of the Pinocchio story).
Rubbing the finger alongside the nose can indicate disagreement. It may also be a semi-suppressed nose-scratch related to lying.
Pinching the bridge of the nose can show the person is evaluating something, usually negatively and with some frustration.
Fiddling with the nose or pressing it down can just be a habit when the person is thinking.
Hirsch, A.R. (2003). Physical and Verbal Signs of Lying. Directions in Psychiatry. December, 2003, Vol. 23, pp. 15-19.