Iran would almost certainly use them. Given the proximity of Israel and Iran, in any nuclear engagement the odds of winning favor whoever launches first. Thus, in every flare up of hostilites the temptation to push the button before the other side does becomes greater and greater. Eventually, given the mutual suspicion and hostility between the two, the decision to launch by one side or the other becomes inevitable. And probably sooner rather than later. I’d speculate that nuclear war in the middle east is a certainty within 10 years of Iran getting the bomb.
That's a reasonable assumption, given the fact that they've stated for years and under multiple governments that the reason they need them is to use them.