At best, Iran could test a home grown nuke on Aug 22. If they intend to shot a missile based nuke, they are using someone other country's components. Designing a working nuke missile isn't all that easy.
Making a nuke is tough, making a small lightweight nuke is tougher still. Lots of testing needs to be done to get it right. We haven't seen nuke tests carried out in Iran that I am aware of.
Pakistan has working nukes, and working missiles to carry them. The head of the Pakistani nuclear program is a fanatical Jihadi and sold the plans to multiple Muslim nations. He is a national hero in Pakistan, so he was only placed under house arrest when he was arrested. He made a public confession and "apologized".
It is widely believed that North Korea has sold missiles to Iran.
Put the two together, plus enough fissionable material, and you have a nuclear armed Iran, plus the means to deliver.
It may all be "sound and fury, signifying nothing", but a bluff can backfire politically. If Iran is bluffing, then Ahmadinejad may have talked himself into a corner he cannot get out of without a huge loss of face.
I hope that is what he has done, but I doubt he would take that chance.