Did I make a mistake?

I passed my test last Thursday and went driving by myself for the first time this morning, but I’m worried I did something wrong. A bus stopped at the bus stop so I stayed back and looked round, saw there was nothing coming and decided to go round it and move back across. To my surprise, after 20 seconds or so I looked back and there was a massive queue of cars behind the bus, even though there was no traffic coming. I assumed that there was nothing wrong as I safely overtook the bus, but the queue of cars behind the bus made me question myself. Did I do anything wrong?