How do I edit site navigation spacing?

Site URL: http://www.tommorsebrown.com

Hi there,

Take a look at www.tommorsebrown.com - you can see the padding on the right side of the navigation doesn't align to the right side of the portfolio squares. It does however on the left side of my site name. How do I move the nav to the right?

Add to Design > Custom CSS

div#mainNavWrapper {
    flex: 1 0 100%;
}