Booger cheese is the crust from a pulled booger that is left on the face or cheek.

Or

A crusty booger left on clothes or on the wall of a bathroom stall.

Or

A booger that has been flicked on the back of an unsuspecting pedestrian crossing the street.
After wiping his nose, Tommy left the remnants of a booger on his cheek.

"You need to clip them nose hairs before you get that booger cheese on me Nicca!"
by Lil' Dookie October 30, 2013
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