It’s possible that the early experience makes you more cautious around people than most. Yes, the other kid was inappropriate. But it doesn’t sound like you were traumatized by the event. He was a peer, not an adult who betrayed your trust. You told. You were believed. He got in trouble. It didn’t happen again.
So I think it’s more likely you are going through an absolutely normal and difficult part of being a teen. Most teens tend to have friends of the same gender at first. Most are awkward around the other sex until they get the hang of it. Most teens struggle with lots of questions and concerns about what it will be like to be in a relationship. It’s usual to wonder how to kiss without bumping noses or locking braces. It’s normal to be confused about how much to share with another person and when.
But here’s the important thing: Most people figure it out. Oh, some people seem to have it all together by the time they are 12. Other people are still working on it well into their 20s. But most do come through this stage okay to more than okay.
The way to get more comfortable is to get more pracice being around people. It’s usually helpful to join up with an organization or club or activity that you genuinely enjoy where other kids your age are involved. When people are engaged in something they like or believe in, it’s easier to talk to each other because the focus is on the activity instead of on each other.
I’m glad you wrote. It’s hard to sit with worries like this. I hope you find this answer comforting and encouraging.
I wish you well.