Changing region

This is my first time using an iPhone, when I newly acquired it last month, I enjoyed every bit of it as I had just switched from using android devices. However my problems all started when I wanted to start my Apple Music and pay for it. I had to input my master card details and all through my Apple ID. So mistakenly I paid an amount of 2000 Naira in Nigeria currency to my apple account, all in the bid that I can use it to purchase some paid apps and also use it for my Apple Music, but that was were the issue began, I guess my region was chosen as the United States while am in an African country, Nigeria. Now I tried changing, but it’s telling me that I have to spend the money on the Apple account first before I can change it, but how am I expected to spend it when all it tells me is change region anytime I wanna purchase something.I can’t even download any app from the App Store because of this. Please help me out, am so confused right now. I’ll send some screenshots so you understand better.