Need Help Fast NSFW

So I just found these tiny bumps at the top of my butt crack. They aren’t super red. They are only kinda itchy. And they aren’t anywhere near my anus or vagina. I’ve never had these before. I tried googling some answer but we all know how that goes. Could it just be a heat/friction rash? I worked today in leggings and a thong and was sweating most of the day? I don’t have any known stds (I’ve been checked). But I’m worried because I purchased my leggings from someone off the internet and didn’t think to wash them before wearing them. I hope they didn’t give me something. Any advice or ideas would be extremely helpful!!! Thank you!!!