That's one of the strangest parts of the Bible, IMO. Why, in that scenario, would nudity have been "bad"? I mean, talk about terrible writing: whoever came up with this idea was... trying to explain why people have to... wear clothing? And that was his best guess? "nudity is evil"?
Even if we accept it as a metaphor of some kind, it's awfully clumsy. Adam and Eve gain the ability to discern right from wrong, and their first thought is "whoa, we're naked!" Really? You mean like every other living creature around you?
It speaks volumes. One does not even need to get to the global flood a few chapters later to realize it is all a mythological tale used to try explain things. Jewish mythology is no different then say Greek or Norse mythology.