Big fingers.
Explanation: This joke is funny because it prompts the listener to think about the absurd relationship between large fingers and large nostrils. The implied conclusion is that if someone had large fingers, they would need larger nostrils to accommodate them, suggesting that gorillas might pick their noses. The humor arises from the unexpected and absurd imagery, as well as the insinuation of a common, somewhat silly behavior. This clever twist creates a playful connection between physical attributes and humorous behavior.