It can have several significances of unfathomable depth and wisdom. One of them is that Jesus indicates to the Personhood of the Spirit, for wind cannot wish anything, for it blows automatically, while when "wind" is used metaphorically as referring to the Spirit, it indicates that birth in Spirit is not automatic, but it is based on reciprocation of the born - man - and the Birthgiver - the Spirit, Who blows where He wishes.
However, the sentence "and so with everyone who is born of Spirit" can have another meaning as well: only the Spirit-endowed man is really free and "blows", that is to say, speaks and acts without being influenced by tyranny of fears, sinful passions, earthly/limited interests or rigid ideological mindset; since such a man possesses the Spirit, that is to say the Mind of Christ (1 Cor. 2:16), then his words and actions are strange to the world, ununderstandable and even hateful for the latter. But a Spirit-endowed man is totally free and acts at will, or rather co-acts with his inspiring Spirit, for where is the Spirit of God there is freedom (1 Cor. 3:17).