Nuclear weapons are of no use in the Middle East
If Iran were to use them against Israel, they will also kill millions of Palestinians and Arabs from the neighbouring countries. Not necessarily instantaneously, which will make things worse for the country that used the Nuclear bomb.
Using nuclear weapons is still out of reach to small terrorists groups (if it were not, they would have used them) or else, knowing very well what the consequences would be and their counterproductive use, they rely on other means.
A very important first step towards peace would be for Israel to recognize it has the bomb and is ready to disarm it and have this checked by international experts. Iran will have to do the same, otherwise they'd lose face.