I was just 11

Now I'm  17-year-old girl but now i remembered that I was sexually assaulted by my cousin when I was just 11 and didn't understand what happened with me, that time he was 13 or 14, after doing that I only understand that he done something bad so i asked him "why did you do that to me" and he answered "So what you are my sister" like seriously. and I also remembered that in 2021 when he was moving to America, we throw a Dawat(gathering in South Asia) for him and he was touching my hand weirdly, In 2022 he kind of harassed one of my cousins by telling her about corn, etc. I don't know what to do and i can't even tell this to any of my friends like how can i share this to anyone? and his parents will never believe me and my that cousin also our grandparents love him more than any of us. He has a bright academic record and people love him so much. I pray to Allah to punish him for what he has done and is doing. His mother is single mother, he should have looked at his mother before doing this, if the truth comes out as one that his true face will come out his mother, I mean my aunt will be in ashamed but she is a nice person, and I don't want her to be sad.  
Please anyone suggest me how to forget this things and move forward.