Hello, I have a road bicycle here. It was working fine until suddenly the left pedal locks up.

Now, this is just the pedal itself, it stops spinning so I can't continue pedaling without having to lift my foot up and off the pedal as the pedal will not spin with my foot. I have to get off, spin it back the other direction and then repeat the process.

Not sure how this happened or how to fix.

Any ideas, thanks!