Gaze at the tip of your nose. No doubt it feels a bit strange to do so; you will probably see a fuzzy cloud protruding from your face which seems to shine quite a bit. If you close either eye, the orientation of this fuzzy shiny cloud vis-a-vis the background shifts too.
So far so good. However, now consider, or try to see, this nose not as protruding from “your face,” but as emerging from a void. This void contains everything: your nose, the bits of cheek and lips you can glimpse, your body, the surrounding environment with all its colours and smells and sensations and, if we pay attention, your thoughts, feelings and sense of self.
All emerge from and dissove into the void.
Forget navel-gazing. Nostril-gazing can trigger pretty powerful meditation and insight.