I got assaulted by my co-worker what can i do?

Tell your boss that this kind of behavior is really making you uncomfortable. The guy could attack you again or attack someone else. It's bad for the work environment for him to be around. If that doesn't help, go talk to a labor lawyer, he will have advice on what to do in a case like this, You can get a cheap session with a lawyer by contacting your local county bar association and asking for lawyer referral.