image is being used by stopped container

You can also use --force , -f Force removal of the image

If you use the -f flag and specify the image’s short or long ID, then this command untags and removes all images that match the specified ID.

  docker rmi -f <image_id> 

Note: this command removes images being used by containers.

You need to delete the stopped container with docker rm, and then you can delete the image it uses with docker rmi.