Since arriving in the Jupiler Pro League from German side Wolfsburg in August, the 19-year-old has scored seven goals in 12 games for the club.
His impressive form earned him a recall to the Super Eagles squad for this month’s 2019 Nations Cup qualifier against South Africa and he started in Tuesday’s 0-0 friendly draw against Uganda in Asaba.
At Charleroi I have comfortably found my happiness again, and I thank everyone in Belgium and at Wolfsburg for the opportunity and support
“My confidence level was very low at some point and what going out on loan to Charleroi has done for me is unexplainable,” Osimhen told BBC Sport.
“It was tough in Germany because of the high expectations – some people started doubting me and also pushed me to start doubting myself as well.
“The football in Belgium has helped, I also have a wonderful group of players around me and the coaching crew have been great with me.
“As a young player, you hear people comparing you to other stars who emerged from the under-17 World Cup and never fulfilled their potential.
“But now at Charleroi I have comfortably found my happiness again, and I thank everyone in Belgium and at Wolfsburg for the opportunity and support.”
Osimhen was the top scorer as Nigeria clinched a fifth Under-17 World Cup title in 2015 with 10 goals in Chile, which saw him win the Golden Boot and Silver Ball.
After the tournament he decided against joining English side Arsenal, to sign with the 2009 German champions Wolfsburg in January 2016, but injuries restricted him to 16 appearances for the club in all competitions.
Despite being a part of the squad for two years, his lack of games meant he missed out on going to the 2018 World Cup with Nigeria.
“I am still young and I think it wasn’t meant to be, but I can still look forward to the future,” he added.
“I thank coach [Gernot] Rohr for the opportunity to return to the squad and I hope to keep working hard to stay in his plans.”
His 10 goals at the U-17 World Cup eclipsed the previous best of nine set by Ivorian Souleymane Coulibaly in 2011 and Florent Sinama Pongolle of France in 2001.
Osimhen was also part of the Nigeria side that won the Under-23 Africa Cup of Nations in Senegal in November 2015, which also qualified them for the 2016 Rio Olympics.
His exploits saw him crowned the 2015 Confederation of African Football (Caf) Youth Player of the Year .
He has played for Nigeria at all levels, from under-17 to the full senior side, for whom he has won three caps.