Many years ago..I was the manager of a Montgomery Ward Auto Express. MW sent me to the Michelin tire plant in South Carolina for tire training. I learned many things about tires and what you had was known as in "impact/pinch break" to the inner rubber liner of the tire casing. it is caused by many things, chiefly curb strikes but also potholes too that were not enough to make the tire fail immediately but caused a small break in the liner as the rubber was pinched between the rim edge and the hard surface you just hit. A person so "vehiculary afflicted" would get out of the car, look at the tire and be thankful that the tire was not shredded. The problem is that once the pinch break was created, air would begin to leak through it to the outer casing of the tire and cause the slight budge (also called an egg bubble) in the sidewall. The leaking process would take 1-2 months of driving to create the bulge in the sidewall and typically, the car owner simply forgot that they hit the curb/pothole and want to claim a defective tire.
PS: The last place you would take a tire for defect/warranty inspection is the car dealer where you bought the car. You should contact the tire manufacturer and ask them where (tire retailer/service center) you should bring the tire to for inspection.
The old story goes that car manufacturers want three things in a tire for their cars..they want them black, round, and cheap and the first two don't really count.