Thanks for the question.
It is a lie, but a venial lie. The bigger problem is that it may reveal you have a problem with honesty when it comes to how people perceive you.
- Do you find yourself being afraid of being judged?
- How is it that you want people to perceive you?
The answer should be as you truly are, nothing more, nothing less. We all often worry too much about how we are seen by others, but God sees us for who we are, in all our imperfection. Strive for perfection, but get used to falling short because that is where most of us are.
This lie did not invalidate your Confession, but you should bring it to your next Confession anyway so you can practice honesty.