Remove tag

I have setup a private registry by nexus oss and I have setup a docker hosted repo on it.
I must use nexus ip address to push images into repositry and before that I must tag the images with the repo ip and port number.
on the other hand on docker client I have set the damon.json to use my insecure private repo and port number and I must write the complete repo:port/imagename to download images on the docker client.
I don’t want to save/store the images with the complete repo:port/image-name, because when I setup cluster such as kubernetes, it needs only image-name is stored and it doesn’t detect images named reponame:port/imagename.
there is one way to download images and then retag them locally but i don’t need this solution because i must do it manually.
I want to store images like the way when i download images from docker hub and only imagename is soted on the docker client.