You can say "sorry about being short with you yesterday. I was tired" and chill out. You're very nervous. He's a guy and there are billions out there. If you act really nervous, he might get nervous. Just be yourself. Talk to him like you would talk to your friends. Just be you.

Here's the funny thing - he is probably as nervous as you are. Trust me, he will appreciate it if you reach out to him. Right now, he is probably wondering what happened and if you contact him it will be as big a relief to him as it will be to you - or not. Frankly, I am dubious about relationships started on Facebook. You can't really know someone, let alone get to know someone, electronically. Facebook and the like create the illusion of intimacy without creating the fact of it. So go into this with a "nothing ventured, nothing gained" approach. Exchange some pleasantries, talk about things you like to do in common and such. If it turns out there is something there, than hint that you would like to do that thing - seeing a movie or whatever. It does not have to be subtle - in fact it probably should NOT be. Say, to him, "Hey, it would be great if we could go to a movie sometime.") If he asks, you are on your way. (I am just old fashioned enough to believe that the gentleman should do the first asking. Later, as you become better friends, then at that point you SHOULD - from time to time - do the asking.) Most of all, quit overthinking this. It sounds cliche, but be yourself and be honest. Say, "Hey, I really enjoyed talking (or texting or whatever they call it) the other day. Sorry I had to be brief. How are things?" Don't explain why you were brief, just apologize for it and move on.