Braces anyone relate?💞😢

So i got top braces put on two months ago now i got my lower ones as well.. today when i got back from ortho i brushed my teeth and realized cold sensitivity with the toothpaste on one side? Why is that normal never happend without braces is somethng wrong? Is it the toothpaste or is somethng wrong with braces or is it totally normal it doesnt bother me alot but still im worried