Tighten a loose bolt? You mean a loose nut don't you? The thing there with external threads is a axle.

Here are your pictures....









Several more here...... https://www.bikeforums.net/g/album/37192031 Don't drop a wrench on that bare foot! <grin>


If that is a new bike or even a year old, you probably should go to where you bought it and let them fix it and then show you everything you need to know abut removing wheels, reinstalling them and properly adjusting the quick releases.

Many, probably will do this for any person that comes in with any bike of any age. Whether they sold it or not.