While many countries have nuclear weapons, has a war ever happened between two nations that had nuclear weapons (but obviously chose not to use them). For example, there was a lot of tension between the Soviet Union and the United States, but no shots were ever fired. Other wars that I can think of recently have only had nuclear weapons on one side of them.
Follow up question: If the answer is "Yes" to two warring nations both having nuclear weapons, how serious was the consideration to use them?
No there hasn't unless you count the undeclared Indo-Pakistani War of 1999 also known as the Kargil War.
Pakistan has a policy of using nuclear weapons if they are unable to defend conventionally against invasion like in 1971 or if they were struck first. India had declared it would only use nuclear weapons if they were attacked with nuclear weapons first.