If you are not confident in your ability to diagnose the problem call a local garage door service company.
Garage door opener sprocket broke off.
The chain wraps around this sprocket as well as the gear and sprocket at the motor.
Chain driven garage door openers should have some slack in the chain for optimal performance.
Over time though this slack can increase or the gear and sprocket assembly can wear and the chain may pop off the sprockets.
Chain drive garage door openers have a sprocket that is attached at the top of the motor.
You can put the chain back on your automatic garage door opener using a simple adjustment mechanism.
If the piece of metal that broke off is the piece where the j bar that connects your garage door opener to the door then you can repair this by installing a new operator bracket.
Operator brackets come in different styles some are.
Over time the sprocket s teeth can wear and the chain may jump or skip when the opener raises the door.
This gear kit on amazon.
First we will address fixing the broken piece of metal.
If yours is a belt drive you need a kit like this https amzn to 2zqns.
Sprocket is at the end of the opener rail closest to the garage door opening.