I lost one of my AirPods, I have a warranty am I able to get a new pair?

Typically no,

Assuming you have AppleCare+, you might be able to get a replacement bud for a reduced price. I've included a link where you can help estimate the cost of the repair - AirPods Repair & Service - Apple Support

Cheers!

Apple's Limited warranty and AppleCare+ does not cover lost AirPods. There would definitely be a cost to have it replace. It would be just a small amount lower than what it normally would cost. One AirPods I believe is $69 for AirPods, Pros cost more, but I'd have to double check that pricing...

You can use this link to check the cost:

AirPods Repair & Service - Apple Support