At night, New York, eat a slice too hot
Use my tongue to tear the skin hanging from the roof of my mouth

from Nas (Ft. Large Professor) – Loco-Motive Lyrics on Rap Genius

Meaning

New York is famous for its pizza that is hot and cheesy.

Also, this could be a reference to his song, Represent from Illmatic:

This nigga raps with a razor, keep it under my tongue.

Were Nas to have a razor under his tongue, it could be used to “tear the skin hanging from the top of his mouth”. As in to say he raps in a sharp/intelligent manner.

When you eat hot pizza too hot, it’ll burn the roof of your mouth. Sometimes so bad, that skin will start peeling.
This is what Nas is talking about. Very descriptive.

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