i’m not sure what you’ve done or what you’re trying to do. this is my header:
<header class="site-header" style="background-color: #92A2BA; font-weight: bold;">
<div class="wrapper">
{%- assign default_paths = site.pages | map: "path" -%}
{%- assign page_paths = site.header_pages | default: default_paths -%}
{%- assign titles_size = site.pages | map: 'title' | join: '' | size -%}
<!--
the next line is your 'home' link for the blog (has your name by default, i changed it to say home)
you could put your extra link next to it like this:
-->
<a class="site-title" rel="author" href="{{ "/" | relative_url }}">Home</a>
<a class="site-title" href="http://yourmain.github.io">MY MAIN GITHUB.IO SITE</a>
{%- if titles_size > 0 -%}
<nav class="site-nav">
<input type="checkbox" id="nav-trigger" class="nav-trigger" />
<label for="nav-trigger">
<span class="menu-icon">
<svg viewBox="0 0 18 15" width="18px" height="15px">
<path d="blah blah blah"/>
</svg>
</span>
</label>
<div class="trigger">
{%- for path in page_paths -%}
{%- assign my_page = site.pages | where: "path", path | first -%}
{%- if my_page.title -%}
<!--
these are your page links on the right hand side
you could add your extra link here, either before {%- for path in page_paths -%}
or after the {%- endfor -%}
-->
<a class="page-link" href="{{ my_page.url | relative_url }}">{{ my_page.title | escape }}</a>
{%- endif -%}
{%- endfor -%}
<a class="page-link" href="http://yourmain.github.io">MY MAIN GITHUB.IO SITE</a>
</div>
</nav>
{%- endif -%}
</div>
</header>
does that help you?