Worst case: “Iran has a doomsday device and isn’t afraid to use it” (lots of virgins in Paradise). Who’d be willing to call their bluff, if it was one? And what mischief could they get up to if they were immune to attack?
I say they attack someone in the West. My guess is a small Eastern European country, or maybe even Turkey, with Putin’s blessing. I don’t think they have the balls to attack Israel.