He was subbed on in the second half, he replaced Kelechi Iheanacho of Leicester city.
His goal also end Benin long unbeaten run at home.
Paul could start in the last group fixtures on Tuesday in Lagos.
“I’m happy to have scored the match winner for the team in Cotonou,” Onuachu told The PUNCH.
I’ve worked very hard to get here. It’s like a long road but I’m very happy to be here and to get the opportunity and the goal.
“I want to do more like I have been doing with my club (Genk) this season. It has always been my dream to score for Nigeria in games and I want to do that regularly when I get an invitation to represent my fatherland.
Onuachu is also aiming to add to his tally if he gets a chance against Lesotho in the Eagles’ final Group L game on Tuesday at the Teslim Balogun stadium, Lagos.
“I hope to get another chance to prove my worth again,” he added.
Super eagles will be playing in Lagos for the first time over a decade.