It's a bit late to concern yourself with the matter at this point. You could certainly go ahead and have a conversation with your coworker and apologize for the misunderstanding, but it would probably be a bit awkward. You should have just said something at the particular moment that it happened, such as "Oh, I'm sorry, I didn't realize you were speaking to me." At this point, you are probably the only one who is still even thinking about it. Your boss and coworker have probably not given it a second thought. You sound like you have some social anxiety and a little paranoia as it relates to how others think of you. You should probably get those things under control, otherwise you are going to drive yourself crazy. Remember this: Nobody cares about you. I don't mean that in a negative, hateful sense. Of course, you have people in your life who love you and care about you, but odds are, your boss, coworkers, the butcher, the mailman, and other people who are not a significant part of your life are not among those people. Unless they are mentally disturbed in someway, these kinds of people in our lives do not regularly think about us and do not care about us. When you come to realize that 99% of the world does not specifically care about you, what you feel, and what you think, it will be like a weight lifted off your shoulders.