With the usb stick connected go into disk management and see if it shows up there. In order to do anything with it you would have to have it show uo on the computer. You can always try another computer and see if it will show up there.
You can also shut down the computer and unplug the psu and then start it up and see if the usb stick shows up.
If you can't get it to show up then you may have to buy a new usb stick.