The error message tells you that your current user can’t access the docker engine, because you’re lacking permissions to access the unix socket to communicate with the engine.

As a temporary solution, you can use sudo to run the failed command as root.
However it is recommended to fix the issue by adding the current user to the docker

Run this command in your favourite shell and then completely log out of your account and log back in (if in doubt, reboot!):

• sudo usermod -a -G docker $USER

After doing that, you should be able to run the command without any issues. Run docker run hello-world

Logging out and logging back in is required because the group change will not have an effect unless your session is closed.