Lost old SIM card, am i screwed?

I honestly don't know if this is the correct place to post, as I have never used Reddit before, apologies if I've done something wrong.

I got my sim card replaced a few months ago, and kept my old one in my phone case (don't know why I did that, stupid now that I look back.) I guess it must've fallen out somewhere somehow, and I'm worried anyone could have access to my information. Am I in trouble, and what can I do?

Edit: I have an iPhone if that matters.