I tried using Nigeria in the living atlas but couldn't found it.
We added support in Living Atlas for countries/regions where we had a good set (e.g. at least 5-10) of high quality items focused on that place. We do not have that for all countries, though the "World" region has a lot of global content that covers all countries. We are looking to add support for more countries, such as Nigeria, going forward.
Okay, I was just wondering why it's not on the list when I wanted to make use of it.