Have you ever tried editing your CRM sitemap, only to find that you somehow messed it up to the point where you can’t get in the application because the sitemap can’t be rendered? How do you get in to fix it?

What I recommend is:

1.  Get a solution with a clean sitemap, either from an older version of your solution or set up a trial and create a solution that only includes the sitemap.
2. Go directly to the solution import URLhttps://yourorgname.crm.dynamics.com/tools/solution/import/SolutionImportWizard.aspx
3. Import the solution

Alternatively, try to connect with the XRM toolbox sitemap editor and you may be able to remove the offending area and/or reset the sitemap to default.