The man prison officials say stabbed Tory Lanez multiple times says he thought the rapper was coming to take his life, claiming Tory put a price on his head … and he simply acted in self-defense.

We had a prison phone call with Santino Casio, who was already serving a life sentence when the Tory attack went down … and, while he’s not denying the stabbing, he says it’s not as simple as some might think.

Casio told us he heard rumors through the prison grapevine that Tory had a bounty on him … and, shortly after, Casio ran into him and thought he saw a suspicious lump in Tory’s pocket.

He says he thought it was a weapon — so, he jumped him, hit him and stabbed him 14 times … yet Casio claims he wasn’t trying to kill Tory

He told us the whole situation is unexpected, because he and Tory used to be cool — having a decent relationship while they lived in neighboring cells at California Correctional Institution at Tehachapi.

Casio also says he didn’t walk away from the incident scot-free … claiming he ended up with a stab wound in his leg, which is why he believes Tory had a weapon.

As for whether he regrets his actions … take a listen. Casio sounds a bit contrite, but he’s definitely not fully apologizing.

As we told you … Lanez was stabbed 7 times in the back, 4 times in the torso and 3 times in the head earlier this month. He was rushed to a local hospital for treatment, but has since been returned to prison.

Many have shown support for Tory in the aftermath of the stabbing … including Drake and Rep. Anna Paulina Luna, who’ve asked CA Governor Gavin Newsom to pardon Tory for the 2020 Megan Thee Stallion shooting that landed him in prison.

Tory’s legal team tells us, “The recent attempt on his life was savage and ferocious, underscoring the clear and present danger he faces while incarcerated. Any claim to the contrary particularly from an individual serving a life sentence for heinous crimes is not only baseless but an absurd fabrication.”