Irritation

Ok I'm 20 years old soon to be 21. I recently had my appendix removed or what was left (it burst) and yesterday (April 15, 2008) while showering I noticed that the head of my penis was sensitive. I looked and it was red just below the urethra. It doesn't burn when I urinate and I haven't had sex since my operation. the sensitivity comes and goes and is quite noticeable when its touched by my boxers. i looked today and there are a few more red, sensitive areas around the rim. i'm not sure what this could be, i know i'm std free and any help would be appreciated.