No, don’t worry about it 😀
I like helping people out, and now I understand more, you want the single blog page to show the secondary menu as well.
You can’t assign a menu on the single (post page). A very efficient solution would be thinking this the other way around, assigning the Primary menu with the links ( Home | Blog ), and the Secondary menu ( About Us | Services | ….) and assign it to the home page.
I will look into it, and update you soon inshaAllah 🙂