Tristram's great-grandfather threw a hissy fit about the size of his great- grandmother's jointure (that's the money left to her after her husband dies). He thinks her request is ridiculous. Ever the wise woman, great-grandma insists that it is appropriate compensation because he has a small nose.
But Tristram wants to clear one little thing up. When he says nose, he really does mean nose. It's absolutely not a dirty joke, so don't go there. Don't even think about it. (Anyone thinking about it?)