"Don't know" has infinite possibilities
When one is aware "I don't know" there is much room to learn and know. But when one is unaware of "I don't know" or aware but doesn't want the world to know about the ignorance learning and knowing is limited.
Awareness and acceptance of "I don't know" is like a dry sponge that can absorb much but a mind that is unaware or unwilling to get exposed is like a wet sponge, filled with assumptions and believes - an impediment to knowing without bias.
Spot the moments in your life where you without much awareness of "don't know" seem to answer as if it is known. That awareness can open up true knowing.