What are you doing???

Conversation with one of my students:

K (*giggles to himself*): Miss Lee.
Me: Yes?
K (*giggles*): Nothing
K (*shakes his head like he smelled something weird*): Miss Lee.
Me: Yes?
K(*giggles*): Nothing
Me: K, What are you doing?
K: Smelling my finger.
K (*whispers*): It smells like poo.

EW.