Sold Apple watch after erasing it but my Apple ID still shows up

You need to follow all the steps on this page;

What to do before you sell, give away or trade in your Apple Watch

You can ask apple to remove the activation lock online on this page;

Remove the Activation Lock Here.

Or this;

If you can't remember/gain access to the apple id that paired the watch to the phone.Take the watch and it's receipt with the serial number along with some photo id and any other proof of ownership to an Apple Store and request that they remove the Activation Lock for you.