Summarize:

You can strike the nose of your attacker if they are in front of you or behind you, but the movement you use will vary depending on your starting position.  If your attacker is in front of you, you will need to move in a forward direction. If your attacker is behind you, you will need to attack as you turn to face them. When standing face-to-face with your attacker, open your hand and strike straight forward, hitting the base of the nose and shoving it back.  Throw your weight into the attack in order to apply the most force. This move causes your attacker's head to snap back, pinching the nerves of the upper spinal column and, if done with enough force, causing the opponent to black out. If the attacker is behind you, bend and lift your arm so that your elbow points toward the attacker's face. Rotate your upper body enough to throw your elbow into the side of the attacker's nose. The center side of the nose, on either side, is another pressure point of the body. If you strike hard enough, you can cause the nose to break and the attacker to fall unconscious.
Assess the best way to strike depending on your position. Strike with the heel of your palm from the front. Strike with your elbow if the attacker is behind you.