The universe was very tiny to begin with. I’m quoting here:
Lemonick and Nash in a popular article for Time describe inflation as an “amendment to the original Big Bang” as follows: “when the universe was less than a billionth of a billionth of a billionth of a second old, it briefly went through a period of superchanged expansion, ballooning from the size of a proton to the size of a grapegruit (and thus expanding at many, many times the speed of light).”
But—-if it was possible for anyone to be around at the time and measure it, would they have thought the universe was “the size of a grapefruit”? -or would the massive curvature of spacetime have made the ruler, the observer and everything else correspondingly tiny – so to the observer, the universe always appears the same size?