You're posted on wrong board, move this thread to
Currency exchange to get an user who interested to trade their BTC/USDT to Naira.
Above user who recommend @CryptopreneurBrainboss is a good option too, he's a very known and trustworthy Nigerian user in this forum, he wouldn't steal your money.
I actually know few exchanges that you could trade your coins to local flat. Exchanges like Luno, Paxful and Roqqu are popular here in Nigeria.
AFAIK Nigeria bank is banning Bitcoin transaction, I don't think it's good to use that's exchanges in current situation.