I've broken my new MacBook Pro (with touchbar) like this, do I have to repair it?

You certainly don't need to repair it unless you can't use the device. It's a minor safety hazard until you contain any broken glass, but gravity or a toothpick to dislodge any fragments and then some clear tape should handle that. If you want to put a little black electrical tape over the aluminum inside and then use thin clear tape to make the surface smooth - that would be the advanced level patch I'd recommend.

Neither the one year warranty nor AppleCare extension / expansion of the warranty is intended to cover that sort of damage, but I would still call Apple's phone or web support if you aren't going to be in the area of a store in the next week. Ask Apple what your options are, but be prepared if they don't offer to pay to repair the damage.

Once you have a quote (assuming it's not covered), check with your form of payment. Many US credit cards come with accident protection for new purchases - you might be covered under some sort of protection / insurance to pay whatever cost Apple might charge to repair it.

At that point, you can revisit if you're OK with the tape covering it and know what your options are if the cracks spread or if the hinges were damaged when the pressure built up before the glass gave in and cracked. I don't think that's the case since your photos show that the glass had no backing right where your item was placed and there's no evidence of deformation on the aluminum - so this might be a oops you can live with if you don't want to pay the cost for a new display repair and everything else works properly. All indications are this is cosmetic damage and can be patched well enough to keep further dust from invading the display housing if there's even a path from that lower cover to the main display space.

I would try to make it to an Apple Store before the 1 year AppleCare coverage expires.

But you don't HAVE to repair that. I know someone who put a piece of scotch tape over their cracked glass touchpad and is still using their computer.

I would at least tape it up so the cracks have a harder time expanding.