Should i tattle?!?!?!?!?

Ok so just recently i took my social studies final which counts for like 60% of my grade average. I feel i did really good on it. The kid who sits next to me told me that he cheated off of me, the day after we took the test. I dont mind too much, but the fact that i got in trouble earlier this year for letting a friend copy a homework ignment and took two 60s in my average. Mind u im like a straight A student. So i dont want to be put in the situation where my teacher notices similarities in the answer sheets and thinks i helped my clmate. So do you think it is better to not say anything at all and let it slide, or just to tell on the kid and cover my own a$$? I have 2 weeks left of skool if that counts for ne thing. Sorry its long.