Open up the pc and unplug the USB connectors from the motherboard. They'll be the ones going to the front/top USB ports that you probably used the flash drive in. Most more modern pc's will have 2 connectors, a black one near the bottom right hand corner of the board and a much larger blue one on the right hand side. This is the usb2 and usb3 connectors. If there is any problem with shorts in these, this'll be a partial cure and should get you back up and running. Experimentation will tell you which one needs fixing/replacing. If it's just a glitch, it should fix this too as the pc won't detect any viable USB port until something is plugged back in.
This is assuming you used the front ports. If you used the rear ports, those are direct hard connect to the motherboard itself and will require some luck to diagnose or some serious adjustments in the bios and/or firmware