Giants owner Steve Tisch confessed his Super Bowl superstition on TMZ Live today ... saying he won't remove 5-week old nail polish from his toes because he's afraid it could sink his team. 

Tisch says 5 weeks ago his young daughters painted his toenails red and blue ... and his team hasn't lost a game since -- so now he's afraid to remove the polish.

Tisch adds ... he's barely washed his feet since his girls shellacked him -- and he has no plans to clean up ... at least until after Sunday. 

This little piggy went to the Super Bowl ...

NY Giants co-owner Steve Tisch has 2 things no one else does -- a Super Bowl ring AND an Oscar! He also has the cajones to tell us he'd actually choose one over the other!!