I am a bit worried that your response to having made an invalid assumption is to think:
should I just go on with my life with the notion that no one will likely read my thesis
What did you just spend the last 4 years (or more) of your life doing? Your thesis topic is (in theory) the culmination of years of work learning how to apply the scientific method rigorously. If your hope is that no one will read it.... What have you done with your time? Most of the professors that I know in biochemistry post doctorate work, and into the majority of the career was related to the work they did in their thesis.
Why am I worried about this?
What have you been wasting your life on that you hope no one will read your thesis? It should be a major accomplishment that you are proud of, that will help you as you start your career as a scientist.
As you apply to your first job with a PhD, Every single person you interview with will want to talk about your thesis work. It is the capstone of your PhD.
When you talk to them about your thesis, which do you think sounds better?
"I made a mistake in my thesis, but I assumed no one would notice it and am glad that it is over. You should hire me because that is what I bring to the table... A person that makes mistakes and hopes no one will notice".
Or "While going over my PhD thesis, after it had been accepted by my universities library, I realized that I had made a mistake. And I then went thru the (however challenging process it is) to file a correction. I am not perfect, but I am honest, I admit when I am wrong and fix my mistakes." It becomes a talking point that you can use when someone asks you "Have you ever made a mistake and what did you do?"
What am I saying?
I don't want to be judgy... But I worry that your question was "Should I hide the mistake I made, or not" instead of "How will this mistake effect me/ what can I do to mitigate the impact it has". It makes me worried because one of these is an ethical question: Should I be dishonest and hide a mistake I made... Or should I not. And one is the question of someone who made a mistake and wants to know what they can do to mitigate the impact it has on their career.
At the end of the day, making a mistake on your thesis, while it would have been better to not make a mistake, is not a big deal. You followed your schools process and multiple people looked at your paper and didn't see the mistake. You are at the start of your career no one expects you to be perfect. But ignoring the mistake and hoping that no one will notice is a big deal... I can guarantee that your thesis will get at least cursory glance by anyone who is really interested in hiring you as a postdoc.