Where to proceed after accidentally sibling-zoning someone?

I apologize in advance- this is really long, but if you like giving advice, I would really appreciate it! Normally I’d talk this kind of stuff out with my best friends from back home, but they’re pretty difficult to get ahold of since this is freshman year of college and everyone’s busy with classes and sororities and whatnot.

So there’s this guy. We became friends a couple of months ago. He acts very immature sometimes- like an elementary school kid, poking and tickling people and chasing after birds when he sees them in the park. I kid you not. I used to think I could never see him in a romantic way, because he felt like such a little brother to me. I would actually say it to him- I’m taking Korean and he’s Korean, so to practice I’d call him my 동생, which is younger sibling in Korean. He’s even called me 누나, which means older sister (but he doesn’t anymore).

Then, after hanging out with him and seeing his serious and mature side…. well, we get along really well and a lot of our perspectives align so we don’t actually fight about anything other than the fact that he pokes and teases me (but he does this with everyone so it’s not his way of flirting). I’ve hung out with him every day this week and last night, I stayed up four hours longer than I intended to, just to talk to him. Yeah I like him.

Now I don’t know what to do. I really suck at flirting, otherwise I would do that, and drop hints that I’ve changed my mind about the whole little brother thing. I’m very shy and introverted when it comes to talking about my feelings- but he likes to say stuff straight out so I know he’d appreciate my honesty if I told him. I’m just afraid of ruining our friendship since we have only known each other for a little while. Also I’m freaking terrified of rejection.

I don’t think he sees me that way anymore because he’s talked to me about girls and how he wants to meet more girls and hook up and all that stuff, which isn’t as easy for me because at my college, the girl to guy ratio is already pretty high, but then about half of the guys are also gay. I don’t have many other opportunities and I really like this guy so I don’t want to let him go.

I want your honest opinion. Is it too late? Should I come out and say it or move on? I’m just at a loss here, sorry.