Help me please

I’m not sure who I should talk to about this and I am so confused.

So when I was about 11 I moved states but we came back just after Christmas for my parents friend (Jim) was having his 50th so we decided to fly back. Later on I went and stayed with Jim and his wife Maddie (I was very close to maddie she was like a second mother to me) anyway she had 3 boys (all much older than me). The middle boy let’s call him Hunter was about 10-ish year older than me. The day of the party he started slapping me on the butt, disrespected my privacy , he followed me around and stuff. While l was at the party I didn’t feel so well so I decided to go upstairs and lay down a couple hours later Hunter came up he asked why I was upstairs and I told him that I was not feeling well. Then out of the blue he started talking about relationship and boyfriends and if I wanted a boyfriend then he started to lean forward like he was gonna kiss me. I moved to the other side of the bed and said I was going downstairs to get food then I ran downstairs and locked myself in the bathroom trying to make sense of what happened. Why has he leaning forward and did he try to kiss me. I went to the party and stayed with my parents most of the time and avoided Hunter. I am home now and I probably won’t see him until the next time we visit in a couple years. I don’t know who I should talk to about this and I am so confused. I need your help please