Don't worry, this is a day at the beach compared to the Cuban Missile Crisis. We were only 24 hours from bombing Cuba when Kruschev decided to pull the misiles out of Cuba. A number of catastrophic scenarios could have unfolded if we had been forced to bomb Russian missiles and soldiers in Cuba.
You're probably right, my biggest worry is a nuclear free-for-all if Iran nukes Israel, so Israel nukes Iran, and then Russia or China nukes somebody, and somebody else decides to use the chaos to deal with an enemy... etc.