chuck (one) under the chin
To touch or stroke one affectionately under the chin. I chucked my daughter under the chin and pulled her close for a hug.
chuck someone under the chin
to tap someone, as a child, lightly under the chin, as a sign of affection. He said hello to little Mary and chucked her under the chin. Please don't chuck me under the chin! I am not a child, you know!