The planet Earth is, to a good approximation, a perfect sphere. But, it isn't perfectly spherical.
Space-time in the universe as a whole is, to a good approximation, perfectly Euclidian. But, it has some curvature.
The magnitude by which the Earth differs from being a perfect sphere (in relative terms) is roughly similar to the magnitude by which the universe differs from being perfectly Euclidian. And, both on average and at the greatest extremes, Earth differs less from being perfectly spherical in relative terms, than the space-time of the universe differs from being perfectly Euclidean.