I bought my AirPods less than three weeks ago at Amazon, I changed my mind about warranty can I still buy it thru apple?

See the following from AppleCare Products - Headphones - Apple

How to buy

1. Purchase AppleCare+ with your new headphones.
2. Or buy it within 60 days of your headphones purchase:

• • Online
  • At an Apple Store (inspection of headphones and proof of purchase are required)
  • By calling 800-275-2273 (requires you to provide proof of purchase)

Hello Peter,

Try this link: Buy an AppleCare plan [was: Can I buy an AppleCare plan for my device?] Click here --> https://support.apple.com/HT202702

I hope so. You’ll need it.