Ronda Rousey - her mouth is so messed up from the beating, she still can't eat an apple.

Ronda Rousey says she's still "really f**king sad" about her loss to Holly Holm -- and says her mouth is so messed up from the beating, she still can't eat an apple. 

The UFC legend is finally breaking her silence about the shocking defeat at UFC 193 -- and told ESPN (via People) that her teeth are still very unstable from all of the shots she took to the mouth. 

When asked specifically about when she'll fight again, Ronda said ... "It might be three to six months before I can eat an apple, let alone take an impact."

UFC honcho Dana White says when Ronda can get back in the octagon, she'll definitely rematch with Holm. 

As we previously reported, Rousey got medical attention in the hours after the fight -- and White says her busted lip already "looks awesome" after undergoing surgery.