What Of It Meaning

(idiomatic) So what? Who cares? Expresses disinterest, disregard or lack of concern.

Example:   Yes, I ate the last cookie. What of it?
1912, Stratemeyer Syndicate, Baseball Joe on the School Nine Chapter 1
  "Hiram took my snowballs."
  "Aw, what of it, kid?" sneered the bully. "There's lots more snow. Make yourself another set and see what you can do."