According to Big Bang theory, your so-called "void" does not exist, nor has it ever existed. There wasn't an infinitely small dense particle suspended in a void, but absolute nothingness (in non-scientific terms). No space, no time, just a singularity that somehow began to expand, creating space and time as it expanded.
Matter wasn't ejected from anything. It was contained within the singularity, and spread apart as the singularity grew, since the space was created as the singularity grew, and the time that was created enabled the matter inside the growing singularity to move.
It took me a while to wrap my head around it, but you'll get it eventually. Most people try to think of a singularity and fail (since it's infinitely small and we aren't capable of comprehending infinity properly), so they do the next best thing, imagine something really small. However the problem with this is that the only way they can imagine something like that is to imagine it in the context of space, such that it was suspended in space. This isn't the case. At that point in time (i.e. the beginning), there was no space, only the singularity. When this expanded, it didn't expand into space (since there wasn't any), but it expanded as space.
Matter wasn't ejected from anything. It was contained within the singularity, and spread apart as the singularity grew, since the space was created as the singularity grew, and the time that was created enabled the matter inside the growing singularity to move.
It took me a while to wrap my head around it, but you'll get it eventually. Most people try to think of a singularity and fail (since it's infinitely small and we aren't capable of comprehending infinity properly), so they do the next best thing, imagine something really small. However the problem with this is that the only way they can imagine something like that is to imagine it in the context of space, such that it was suspended in space. This isn't the case. At that point in time (i.e. the beginning), there was no space, only the singularity. When this expanded, it didn't expand into space (since there wasn't any), but it expanded as space.
