Duuude! See, I am not a doctor. But it looks a lot like my experience. I had a moderately tight foreskin and I developed a rash-like thing right after a couple of days of my first unprotected exposure. It created a little bit of burning after urination and redness all around the glans. It took time but went away on its own. Mine was a case of balanitis, a fungal infection. The doctor told me to keep the area totally dry even after urinating. Although there are a lot of medicines for acute balanitis, I will ask you to talk to your physician first. I don't think you have got an std.
Wish you all the luck.