Although the origins of the snot bubble in anime is unclear just like the origins of the snot bubble in manga is unclear, but the earliest known use in anime is a Norakuro short that I watched on YouTube a few days ago and it was from 1937:
To put simply, it's just a bubble coming out of Norakuro's nose that is later used in anime through later decades, This short is based on the Norakuro manga, though, are there any other earliest known uses of the bubble coming out of the character's nose in anime?