The question here is, what can we do about it? It’s obviously not in the interest of most nations to have a bunch of religious crazies with The Bomb. There’s the argument to be made for the freedom of soverign nations, but that’s another discussion, let’s assume we have no moral qualms about doing what we can to ‘fix’ the problem.

1. Bomb nuclear research facilities. Assuming they’re not underground we can take them out, probably flare up hostilities in the area and perhaps provoke some terrorist attacks here. Best case, we set them back a few years in development and they move underground where we can’t bomb them. Worst case, we don’t accomplish anything and now we’re in open war with them.
2. Skip to the open war part first. Move in and liberate the country Iraq style. Cue indefinite occupation, destabilized country, chaos, American casualties,and maybe add half a trillion dollars to the national debt. Nukes problem is solved, new problem is worse.
3. Destabilize the country CIA style. May or may not work, it certainly looks like we’ve been trying at this for a while with minimal success. Seems to have the fewest downsides of the options. Worst cases, either nothing happens, or the new government hates us even more (is that possible?).
4. Do nothing. Iran successfully develops a small number of nuclear weapons and starts a MAD situation in the area with Israel. While MAD ‘worked’ between the US and the USSR it seems like tensions run a little hotter in the middle east and the situation may collapse badly. The prospect of real consequences may also cool down the constant simmer of conflict. Who knows when religion is involved though.