This is the seal washer for the needle. I don’t recall why there’s two parts to it. I think mine only has one. It seals between the machine and the top of the pod.
This might work to fix it: https://www.amazon.com/Replacement-Needle-Silicone-Gasket-Keurig/dp/B01GYOOUEM
https://www.bonanza.com/listings/Keurig-2-0-Replacement-Upper-Needles-Seal-Silicone-Gasket-K200-K300-K400-K500/767922448