It was the 19'th century French mathematician Poincaré who argued, correctly, that Mathematics is a human construction but not an arbitrary construction. A mathematical theory arises from experience -- experience of the world, of science or experience of mathematics itself. Such a theory can be tested in two ways: (i) it is tested for rational consistency -- this is why proof is so important in mathematics -- but consistency is something which also arises from experience; (ii) it is tested by its use -- a theory which does not solve any significant problem is quickly forgotten.
Mathematics, though a construction, refers to objective truth to the extent that it corresponds to the real world and helps to solve real problems.