I went outside only in socks, and suddenly my feet stung; still in pain, there are splotches all over my feet?

I live in FL; I went barefoot outside to walk my dog real quick, and I figured it was okay to step out in the gr/weeds, but it felt like I stepped on a bunch of teeny tiny tacks or I had a million splinters. The pain is prickly, and there are red splotches on the top of my feet and white round ones like insect bites everywhere else on the undersides. I'm guessing I stepped on prickly weeds? My dog wasn't bothered. I ran cold and then hot water on my feet for a long time and then hobbled back inside to put peroxide on. How can I make the pain go away and should I be worried if this is something poisonous? I have a bunch of ants out in the yard, but I've never had anything like this; I even sat down right after my left foot flared up and nothing bit me. Does anybody know what the heck this is?