To enable the local Nexus 3 private docker registry, you should follow instructions in the website: https://www.ivankrizsan.se/2016/06/09/create-a-private-docker-registry/
And, you can create a new file /etc/docker/daemon.json with the contents { "insecure-registries":["host:port"] }
and then restart docker daemon by doing:
$ sudo service docker restart