Horrible at guy at work; what 2 do?

hi. i work in a big depratment store, theres this guy hes about 25+ hes not british born, from india i think. recently i found out he complained against me, for not working effieciently which is lie. when i found out it was him i was furious. so today when i seen him at work i didnt even want 2 say hello 2 him. newy i only work weekends so sometimes on sundays this guy is kinda incharge cz hes bn there a while. he keeps getting in my face n telling me what to do, he doesnt do that with the guys. he speaks to me very rudely and i hate it i tel him straight but then that will just make him complain against me more. n i dnt want to lose my job over a loser. today he started infront of a customer, n i'm not 1 of them girls who doesnt stick up 4 herself. so i said 2 him y was he criticising infront of a customer, it was wrong etc, he immaturely replied 'whatever'. i used to get on with him becz he used to tell me what this other bloke used to say about me, which now i think he has been making up n trying to stir things. the atmosphere on the shop floor has bn so down lately. i want to complain about him but i dont know if it is a serious matter. need advice.. newy, thank u in advance. x