Blank screen with nothing but a folder with a question mark on it??

I was booting my macbook after the macOS Ventura installation, so i ejected the USB drive that i had installed this update on. Then my mac went into a screen that had a folder with a questionmark inside of it. I was confused and googled that the macbook could not find the ”startup volume” which could be an external disk that’s not plugged in. I put the USB drive in and it started working fine again, but should I do something incase i take the USB drive out again and suddenly my macbook doesnt go on anymore? (If there are any grammar mistakes, I am very sorry because english is not my first language) Please help me! 🤞

• Do i have to keep the USB drive in for my macbook to work? Or can I take it?