On this page of our guide to Psychonauts 2, you will find Nuggets of Wisdom available in the first level - Loboto's Labyrinth.
There are 2 Nuggets of Wisdom in this level.
Nugget of Wisdom 1
This secret can be found only when revisiting the stage. It won't show up the first time.
To get to this secret, you just have to open the zipper created from the teeth. When you visit this location for the first time, you will find a passage here.
2nd Nugget of Wisdom
Location: Central Office.
This secret can be found only when revisiting the stage. First you must acquire a skill - Pyrokinesis.
To get to this secret, burn the painting and get to the next room. That's where you'll see the Nugget.