Cracked chin bar - will it get worse?

The crack on the Bezel is quite common as the glass is quite brittle/fragile due to there being lots of open space beneath the Bezel. Apple will more than likely consider this "Accidental Damage", but if you have AppleCare+, then the repair can be performed for a $99 Display Assembly replacement. If you don't have AppleCare+ and Apple won't cover it under warranty, then you could just leave it go until it gets worse (most likely it will get worse). You could put some black electrical tape over the area to help protect it and keep the glass intact. A Display Assembly is very expensive if not covered by AppleCare+.

Unfortunately Apple won't just replace the broken Bezel portion of the Display. I have replaced the Bezel on many of our organization's Apple USB-C laptops, but it is extremely tricky since there are very delicate easily damaged cables located just beneath the Bezel. This is not something I recommend anyone doing without lots of experience working with Apple glass and adhesives.

Also do consider if it gets worse, you can get an external display to use with the machine.