My Grandpa Raped Me...?

First of all I am 15 years old. My grandpa and I have ALWAYS been close. But not close like, kissing, close like we talk on the phone every night and play games together. Last night though, he went too far. He asked me to follow him to his room and I did then he grabbed me and undressed me then raped me. I afraid of him now. What should I do? Tell someone? Please help me.Thank you!