If you are using an allen wrench insert the head of the wrench into socket located on the pedal arm.
Pedal arm fell off bike.
Also the left side is reverse thread so now you will need to replace the pedal and the crank arm since its stripped.
Loosen the pedals by turning the right pedal counterclockwise and the left pedal clockwise.
If you are using a smart wrench place the jaws on the nut located between the pedal and pedal arm.
Crank loose falls off if your crank arms flop with every pedal stroke or if you can wobble them from side to side fix them now before they become irreparable.
The first thing to do is to try and re tighten the crank arm on to the bottom bracket axle.
If your crank arm just keeps on falling off even after you ve asked your muscle building neighbour to tighten that nut as if his life depended on it there is one simple reason.
Oumers bike crank extractor and bottom bracket remover with 16mm spanner wrench bicycle crank removal tool crank puller tool bike crank arm remover spanner repair tools kit 4 5 out of 5 stars 1 101 8 99 8.
This video will direct you to the appropriate walk through for installing and removing the crankset on your bicycle.
Remove the pedal from the socket.