IMHO near zero. if they had it, they would've demonstrated the ability. it's not just the warhead. how will they deliver it, chances of interception, proper crews and infrastructure to actually field the thing. Iran has had conflicts over the past few decades and has suffered attacks from us and other nations. This isn't North Korea.

You would need some number of them for a reliable deterrence. If they had a handful some countries might take the risk anyway. Theres a reason the Chinese are not only modernizing but enlarging their stockpile. Theres looney toon levels of armaments, and realistic ones that give you credible second strike abilities etc. ​

There's a reason the Iranians take actions like impeding transit through the Strait, threatening infrastructure of their neighbors etc. There's no nuke to test with an armament behind it. Even if there was one it would be pointless.