I thought the car's warranty typically excludes the tires, and the tires have a separate warranty that is covered by the tire manufacturer. If so, it is not the car dealership or Chevrolet that can potentially help you.
I also believe it is extremely hard to get any relief under a tire warranty if it does not include road hazard coverage, because most things that go wrong with a tire could be blamed on road hazard or poor wheel alignment, etc.
You are smart to follow up on that, though. Definitely get it fixed or replaced one way or the other. I know sidewalls are typically not repairable, but a tire dealer can tell you for sure if that is an option or not in this case. Also remember that getting a flat in one of these cars can be a big inconvenience because there is usually no spare and a replacement tire sometimes has to be ordered, so don't procrastinate.