Offer a sincere apology
Bad first impressions happen for a variety of reasons; perhaps you were late for an important meeting with a new contact and came across as unprepared. Or perhaps you unintentionally said something offensive or told a joke that was taken personally. Whatever the cause, apologize as soon as possible. You can do this in person immediately or send a short email afterward. Apologizing is direct and will be better than ignoring the mistake. But don’t overdo it; you may unintentionally make a sensitive situation awkward. Once you’ve sincerely apologized, move on.
Don’t be too hard on yourself
As a result of your nerves perhaps you didn’t make as much eye contact as you could have. Or maybe you glanced at your cellphone expecting an important message to arrive. Whatever the case, don’t beat yourself up over it. While the perceived mistake might be magnified in your mind, it might have barely registered in the mind of the person or group you’re talking to. Take note of the situation and be mindful of it going forward; there’s no need to draw attention to your actions. If you’ve learned from it, move on and let it go.