But if you exceed electron degeneracy pressure, you can get more stuff in the same space… Exceed neutron degeneracy pressure, you’ve got problems. Singularity problems.
But that’s a bit irrelevant. If you were to instantaneously materialise nucleon in that space, the other nucleons would be pushed away from it. So teleporting something into something else; your something else would expand, and if not able to do so, explode.