What would you have done if this happened to you?

I'm adding this anonymously because I am a little (a lot) embarrassed that I didn't handle this situation properly, and I'm going to try not to respond in order to remain anonymous.

Anyway I have this coworker who is really touchy-feely and I do not like being touched at all without permission. It really bugs me but I'm a quiet person and I don't want to be confrontational since I'm still fairly new to my job and he has way more years there. Well yesterday I was on my way to the break room to get my stuff to go home when he approaches me. He wrapped his arm around my shoulder and asks me about my weekend and I'm thinking okay, whatever. Then he asks "can I have some milk?" I was confused by this question because it came out of nowhere. As I uttered a "huh?" He put his head near my breast and started to make suckling sounds. I immediately pulled away, I was so disgusted and uncomfortable. I quickly grabbed my stuff and left. I know I probably should of said something to the managers but I was beyond upset, and I hate getting people in trouble at work because I don't want to get someone fired. I know that's a lame ass excuse, but I know jobs are hard to come by. However I feel super uncomfortable about being around this person now. And I feel really dumb for not saying something. What would you guys have done if this happened to you?