LOL Nas didnt "make up" the line, he did repeat it though and it is wrong but he is not the true author of the confusion, but probably read the false fact some where and repeated it in rhyme.
The one-meter-wide nose on the face is missing. A legend that the nose was broken off by a cannon ball fired by Alexander the Great is still in circulation yet firearms had not even been invented during Alexanders time. A second myth is that Napoléon Bonaparte shot it off, as do diverse variants indicting British troops, Mamluks, and others. However, sketches of the Sphinx by Frederick Lewis Norden made in 1737 and published in 1755 illustrate the Sphinx without a nose. The Egyptian historian al-Maqrizi, writing in the fifteenth century, attributes the vandalism to Muhammad Sa'im al-Dahr, a Sufi fanatic from the khanqah of Sa'id al-Su'ada. In 1378, upon finding the Egyptian peasants making offerings to the Sphinx in the hope of increasing their harvest, Sa'im al-Dahr was so outraged that he destroyed the nose. Al-Maqrizi describes the Sphinx as the Nile talisman on which the locals believed the cycle of inundation depended.