Using a syringe you can drop it right into a dab nail. If you’re too lazy to find get a syringe, you can simply let the material inside your broken cartridge drip out onto a piece of parchment or silicone.
If it’s too stable to come out of the cartridge try getting the cartridge warm first. You can quickly run a lighter back and forth on the glass to loosen things up. Just make sure you don’t allow enough heat to build up for anything to vaporize or burn.
Once you’ve got it all dripped out of the broken THC cartridge you can dab it. The material will probably be runny so you’ll want something you can scoop it with. If you don’t have a dab rig, there are still plenty of ways to use your salvaged oil.