I think that command redirected $ docker commands to the docker machine. Now all my docker commands are giving me an error FATA[0000] Couldn\'t read ca cert.
$ docker
FATA[0000] Couldn\'t read ca cert.
What you are looking for is:
eval "$(docker-machine env -u)"
It will unset the DOCKER_* variables.
DOCKER_*
For the record, here's the output of docker-machine env -u:
docker-machine env -u
unset DOCKER_TLS_VERIFY unset DOCKER_HOST unset DOCKER_CERT_PATH unset DOCKER_MACHINE_NAME