Nick Cannon -- Wild 'N Out with New MASSIVE Back Tattoo (PHOTOS)

Nick Cannon has figured out a surefire way to make people forget he once had a Mariah Carey back tattoo ... with a shock and awe tattoo for the ages.

Cannon inked over his old Mariah tat but he wasn't satisfied, so he hit up a Covina, CA parlor and invested 30 painful hours in the chair.

Cannon's business partner, Pep Williams, chronicled the process in photographs, which will appear in Urban Ink magazine later this month.

As for the new tat ... it features a cherub on each side of the cross (representing his kids). The text below reads, "Father, forgive them for they know not what they do."

Possibly a reference to his marriage to Mariah?