It's not really possible to use nuclear blackmail against someone who has the ability to utterly destroy the person doing the blackmailing. The only way a country can use nuclear blackmail is to either be the only one with nuclear weapons, or to have nuclear superiority. Both of which Israel has at this time. If Iran had nuclear weapons, Israel would still have nuclear superiority because it's got the entire nuclear arsenal of the US pledged to defend it if necessary. Iran will never, ever have nuclear superiority over Israel.

The gun analogy is not appropriate to the argument I'm making. Here's a better one: if I was a human with a great big foot, an ant with a tiny little ant gun would not be able to blackmail me, because I could just squash it with my great big foot.

There is one way a country can use nuclear blackmail against a country that has nuclear superiority, and that's the way Israel uses it against both Iran and the US. Israel threatens to use nukes against a country like Iran in an effort to get the US to attack Iran first. This is because the government of Israel gambles on the idea that if Israel used nuclear weapons first, the US would be drawn into the nuclear conflict anyway, because the US is pledged to come to Israel's defense no matter what, and because they figure there are enough people in high levels of the US government who are joined at the hip with Israel that they would ensure that the US would come to Israel's defense no matter what. So far this ploy hasn't worked, but it's not for lack of trying on the part of the government of Israel.