Riley Cooper's Grandma -- He Made His Racist Bed, He's Gotta Sleep In It

N-word hurling Philadelphia Eagles player Riley Cooper isn't getting any sympathy from his own grandma -- who tells TMZ, Cooper screwed up big time ... and it's his mess to clean up.

Riley's Grandma Betty didn't make excuses when we spoke to her ... saying, "[Riley] brought it upon himself and he has to deal with the consequences."

As we reported, Cooper has already taken leave from the Eagles to pursue counseling after his n-word threat at a recent Kenny Chesney concert -- when he said he would fight "every n***er" at the show.

Grandma says Riley was raised in a good household that never condoned racism of any kind -- so she's surprised by his behavior, especially because she says he's never gotten into any kind of trouble before.

That said, Grandma Betty is optimistic about Riley's future, telling us it's good he's nipping this problem in the bud now before it gets any worse.