How to delete a Play store accpunt through system
If you performed a /data wipe (factory reset) on your old phone, you have nothing to worry about; that person will not be able to "automatically" log onto your Google Account. Old phones will always show up on Play Store when you're looking from your PC.

You cannot remove the device from Play Store, but you can hide it from your Google Play Settings from a PC. Just untick Show in menus next to the device you want to hide.