Inside tmux, docker commands won't work without sudo

So apparently the problem was the tmux shell.

The problem occurs when an account is added to the docker group, while still having at least one tmux session open. closing all tmux sessions solves the problem [the group accounts will now be updated in the next session].

solution:

1. kill tmux:

pkill -f tmux

2. open tmux and test docker:

docker run hello-world

now it works fine