During this pandemic I had to suddenly adjust to studying online, we have never attempted this before so it was a whole new experience. I struggled a bit during my junior year and it dropped my average. However, my previous report cards show that I am capable of getting high marks. I wanted to know if that one bad grade will affect my application to university?
One bad grade will not affect your application. No one is going to look at someone who only got one B and think that they can't handle the course load at their university.
So Ree is a great TL DR answer mine will be a significantly longer one.
One B will not crash and burn your application to well known schools.
Also depending on how many lower than average grades you got you might want to look into pass fail. I’ve heard from Yale well known state schools and others that they will not count this very odd year against you and aim to be as accommodating as possible.
Also if any drastic changes were made if you use CommonApp remember to fill out the Covid/Natural Diasters part to explain personal circumstances.