The big bang theory claims an explosion formed the universe.  Therefore we are living inside of an explosion.  However an explosion as we experience it is almost an instantaneous thing. To an observer outside the universe it would be over rather quickly.  Yet we perceive it as billions of years.

Are we creating a universe when we explode a nuclear bomb?

Answer: We are not creating universe by bomb explosion – but destructing it.

The big Bang is referred to as an explosion  because of the fast expansion it caused.