“What happens to an Asian man when he runs into a brick wall with an erection?”
“A broken nose.”
The Brick Wall
Explanation
This joke plays on a really old and pretty offensive stereotype, suggesting that the man's nose is already 'erect', and hitting the wall would break it, while ignoring the fact that a penis is the body part that would be erect. The humor comes from the unexpected and somewhat absurd punchline.