Just tell him you don't like to be called "kiddo". If he does not stop, you can tell him that you will have to report his unprofessional behavior.

If you don't wish to escalate the situation, pick a name he does not like, and call him by it!

If he happens to be leadership himself, maybe you need to be firm and say " I do not appreciate you calling me that, you're an example and my co-workers will follow suit. Please stop".

I really think this is an immature person!

Salam