Dikembe Mutombo -- I Never Gave Biyombo Finger Wag Permission ... 'We Need to Talk' (VIDEO)

Uh oh.

Dikembe Mutombo says reports that he personally gave Bismack Biyombo his blessing to use the signature finger wag is COMPLETELY FALSE ... telling TMZ Sports, "Him and I need to talk."

Biyombo has used the finger wag a couple times during the NBA playoffs -- most recently busting it out Monday night after a block during the Raptors victory over the Cleveland Cavs.

Mutombo says he's seen reports that he had a conversation with Bismack in which he formally bestowed his finger-wagging blessing ... but insists the reports are simply not true.

"I don’t know when did that conversation took place," Mutombo said ... "Him and I need to talk this summer.”

"He claim in the newspaper and everywhere he said I gave it to him. I said, Did I gave him? Was it family? Cosign? But you know what, he’s a young man, man, I let him enjoy the fame. He’s making me famous!”

“I will see him in the Congo this summer so him and I will talk back home with nobody around us.”