Iran knows that whatever L’il Kim achieved, his own technies are busy working on, and he doesn’t want the additional interest into his own program. He’d much rather have the world come to realize that he’s got a collection of nukes after they’ve already been used.

He also figures that the North has been busy sharing technical data on the technological terrors both countries have been working on to the exclusion of pretty much everything else (like feeding the North Korean people, and providing a viable economy in Iran and North Korea’s case).