Worn out square taper bottom bracket spindle?
The spindle looks a little rusty. That may be what is causing the the creak. Try completely removing the rust with a wire brush and thoroughly cleaning the crank and spindle before re-installing.

Be aware that the bolt can loosen slightly in use as the crank 'climbs' onto the square taper. See https://www.sheldonbrown.com/brandt/installing-cranks.html