Guys, he pursed his lips and did a head nod? what on earth does that mean?

he only does that to me, he only purses his lips and head nods to me and I don't know if that means something in a guys perspective? I didn't even get to smile at him yet and he looked straight at me while he was hitting his hand to the other (playing with his hands) and suddenly sucked in his lips (pursed) and gave me a head nod while they were pursed. wtf?
Guys, he pursed his lips and did a head nod? what on earth does that mean?
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