JohnJacob

My sexual history is that I've had two un-protected BJ's. The last one over a month ago. Yesterday I was on a make shift slip-and-slide, wearing only Board-shorts and a t-shirt, with no underwear. Basically it was a sheet of plastic, covered in dish soap and water. It was also in the grass alot. I noticed that the tip of my penis was uncomfortable as it rubbed up against my paints. After I went in, and it hurt, but there wasn't really any thing i could see, ecept maybe some redness (maybe). Later i noticed small red bumps around the urethra, and some on my scrotum. They don't itch, but are sensitive when they rub against my clothes. It does not burn when I pee. Mu question is, is this a STD, or a reaction from something in the soap or grass? Also what would prevent it? How Long should I expect it to last? How would a doctor diagnos it? What would be the risk in not seeing a doctor?? and If it goes away on it's on, should I still worry??