How to remove external hard drive from Time Machine (OS Monterey)

I have a flash drive that I want to use to put a certain document on. I accidentally set up Time Machine with it, but it never worked because the flash drive is not large enough to use for Time Machine. I thought I removed it from Time Machine (it says there is no backup disk selected), but every time I plug in the flash drive and open it, it acts like Time Machine is still going and I cannot put any other documents on it at all. Help???