Apple watch battery swell

If you bought a brand new watch, March 22, 2021, it includes a full one year warranty. Schedule an appointment at your Apple Store Genius Bar and show it to them. They should without question replace the watch - UNLESS there is visible damage to the watch unrelated to the screen coming off the watch.

This is a receipt from an AppleStore or Apple Authorized Reseller where you bought it. And original?

Was I correct that you purchased your watch March 22, 2021? If that is correct, call them again and elevate this higher. There is some miscommunication somewhere.

Take your receipt with you. The watch has a full one year warranty.