Chickle

Chick·le
ˈchik(ə)l/
verb
1.
lightly touch or prod a person under their chin in a way that causes laughter.

noun
1.
an act of chickling someone.

"Dad chickled the baby's chin"

Chicklish

Chick·lish
ˈchik(ə)liSH/Submit
adjective
1.
sensitive to being chickled.

"Babies are chicklish on their chin"