If Iran was able to develop a nuclear weapon and used it to hold the Strait of Hormuz hostage, estimates are that oil would go from $150 to $300 a barrel.
If Iran used a nuke on Israel, Israel as a nuclear power would retaliate. If Gaza is a measure, the retaliation would be a hundred times the intensity of the original attack.
Ninety million Iranian lives would be put at risk. Needless to say, a devastating impact on the entire Middle East.
The impact on oil would be impossible to calculate.
And now you see why we're fighting this war.