same thing happened to me my first year. i figured i just probably wouldn't have close friends again...
but it happened, (took even a little over a year) and now i have two great friends. just give it time.
Don't "join a clique". Just be friendly. Cliques are for insecure people.
Another option would be to embrace your introversion. Just, for the love of god, don't join forces with the cliquey people. They suck. You won't find any happiness there.
If you're interested in joining my anti-clique clique... Clique here.
I felt the same way as you first year OP, I'm the type of person who has a handful of really close friends (though most of those are very long distance at this point, gchat is my best friend because my best friends are only on gchat) and my other interactions are relatively superficial, in that I never went to any parties or any social events, even in undergrad. My medical school class is a) small, b) mostly younger than me and c) VERY social, so I felt like a fish out of water, having been in much larger places (even my high school class was 6x bigger than my med school class) where I could usually find my niche, or if not, just drift around randomly in the cafeteria. However, naturally being pretty introverted (though talkative, yeah, weird, but I was a debater) and being quite content, even happy, doing things by myself, this didn't concern me much. First year I had a few friends I'd talk to, but I never really did anything with people outside of class. However, when we moved to branch campuses and the size of our class got cut 60% this year, plus not having the resources of a larger university town where I could go to random non-medical lectures and events and meet people that way, I have, like someone mentioned, become really close with a couple of people who, like me, have no involvement in the usual med school drama. If I didn't have that, I'd probably go nuts in the current town I live in, because you literally have no social interaction outside of your fellow med students.
So basically, I agree with 'give it time', 'be friendly' (i.e., don't cause or get involved in drama) and 'embrace your introversion', all have worked well with me. Sure, some people might question why I don't go to any parties or social events, but I've never been called out on it and instead do things I enjoy more.