What do you think this is?

Well I really got myself into something that surprised me! See if you can guess what it is. I'm sure the clues will help out. Don't forget you can click on the picture to see a closeup view. I was walking along a creek that my dad owns and I fell into a weed. As I got up I started to have severe stinging and then I started welting up. The stinging lasted for the rest of the day. If I only knew what it was I was by a creek and could of use that to soothe my stinging by washing with the water. Do you know what this is? It is called stinging nettles. I have never heard of it until I fell into it. Here is a picture of it on my arm. This is the 4th day of it. It only stung that day but the redness and swelling was for a week.