No, it didn't affect global warming. The number of nuclear weapons detonated in the atmosphere (a few hundred spread over several decades) is not enough to change global climate in and of themselves. If they had all been detonated over cities, sending up huge amounts of carbon, it is possible they could have had global climate impacts. But they weren't.

The biggest effect that nuclear testing had on global warming is that studying how fallout dispersal occurred, and nuclear winter models, helped lead, through the development of new tools, to the understanding of climate change that we have today.