it means for sure my nigger.
Invented by prisoners who add "izzle" to everything when they are talking on the prison phone so anyone listening wont know what they are actually talking about.

shizzle ma nizzle means "for sure ma nigger"

used by pimps and homeboys as an exclamation of excitement, shock or joy

Read backround written by Weeabix. But can also mean "for sure, my nizzle"

used as an alternative to "fuckin hell!" or "fuck me!" when feeling shocked or startled.

see fo'shizzle my nizzle

To force someone to pay the money they owe you.