Hi and
to the forum Johnny.
First of all, I would suggest you try unplugging the throttle and see if it the motor still tries to run. If it keeps on running with the throttle disconnected, it could be a problem within the controller itself.
If the motor stops when you disconnect the throttle, then either the throttle control or the wiring going to it may be at fault. A poor connection on the black lead between the throttle and the speed controller could cause this fault. Try disconnecting and reconnecting the connectors a few times to try and clean the contacts and see if it helps.
If you have access to a voltmeter, we should be able to hopefully guide you through some simple diagnostic checks to try and pinpoint the fault.
Try the above suggestions first and then report back with your findings, it would also help if you can tell us which speed controller you have as well.
Alan