Iran can't have a secret nuclear program, because if they have one, we would all be staring right at it, so it wouldn't be secret :0 0:
I still say North Korea is a good gauge to go by, when it comes to the pinnacle of fanatical government - with their hands on nuclear weapons: Nothing bad happens, it's a deterent. In Iran's case, it is to deter Israel, which most likely has several nukes.
With a one-on-one situation, we can then look at India and Pakistan, both whom have been quite direct in their rethorics including nukes, and who have also gone through several armed confrontations, including open war, while being nuclear powers, without resorting to nuclear attacks. Again - sworn enemies, full ability to launch and withstand, still showing restraint.
Nuclear weapons are a "dead man's switch", they're a guarantee against an overwhelming attack. Nuclear powers today are very varied, from at-constant-war powers like USA, corrupt holes like Russia, communist superpower China, poor dirthole India, fanatical little North Korea, they all keep the exact same passive strategy with their nukes.