there was no explosion; there was (and continues to be) an expansion
Rather than imagining a balloon popping and releasing its contents, imagine a balloon expanding: an infinitesimally small balloon expanding to the size of our current universe
we tend to image the singularity as a little fireball appearing somewhere in space
space began inside of the singularity. Prior to the singularity, nothing existed, not space, time, matter, or energy - nothing