I believe that the concepts "outside/inside" don't fit that particular situation.
If we say that the universe is "everything" it does not make sense to speak about what is outside "everything". It sounds reasonable, but that is because of how our language works and our concepts fit together in our minds
. If you think of something being outside "everything" then it wasn't "everything" because there is something more...
Matter is created in our perception, which is also the only place it ever exists.