my apple watch is locked under someone elses apple id and it was like that when i bought it

Then you perhaps have bought a lost or stolen watch.

The Activation Lock can ONLY be removed by the original watch owner. The Lock prevents lost and stolen watches from being used. If you bought the watch from the original owner ask them to remove the Lock in their Apple ID. Otherwise, return the watch and get your money back

Remove  Watch Activation Lock -

Go to icloud.com and login

Open Find iPhone.

In the All Devices pulldown menu select your  Watch.

In the resulting sheet that appears to the right choose erase Apple Watch. Select Next until the device is erased.

Then Remove the watch from your Apple ID.

This should reset the watch to the factory settings for you to setup as new and pair it to your iPhone.

M1 Mac mini, macOS 13; Watch, series 7 GPS/cellular, watchOS 9; iPad Pro 2nd Gen, iPadOS 16.1; iPhone 12 Pro, iOS 16.1; TV 4th Gen, tvOS 16.1; HomePods, audioOS 16.1 and Airport Express w/ Airplay 2

Your will have to contact the original owner and ask them to unpair it. (Instructions are below.) Until then, you will not be able to use that watch. If they cannot/will not unpair it, ask for a refund.