First of all there is ZERO proof that Iran is making a nuclear weapon. Even if Iran did make a nuclear weapon, there is zero proof they would actually use it and there is lots of proof they would not. Also, long before Iran could ever "nuke" Israel, most of the Jews in Israel would simply leave. So the bottom line is if the extremely unlikely situation where Iran "nuked" Israel actually happened, only a small number of Jews might actually die.
Israeli troops shoot, injure Palestinian crossing Gaza border fence (Haaretz)