Qur'an 7:22 says: Thus he [Satan] lured them on through deception. And when they tasted of the tree, their nakedness was exposed to them, and they began to sew together the leaves of the Garden to cover themselves. And their Lord called out to them, “Did I not forbid you from that tree, and tell you that Satan is a manifest enemy unto you?”
Some narrations say that, after this occurred, they sewed together fig leaves to cover themselves.
It is also narrated from Imam al-Sadiq (A), when somoene asked about this verse (so you are not the first person!), that the private parts of Adam and Eve were originally not apparent outwardly, but when they tasted the fruit, they became visible.
God knows best.