What Causes Stinging Sensation In Penis While Urinating?

For about a week the end of my Penis stings after urination. I do not get any pain during urination and its definitely not STD's as my wife and I are happily married. I have not had sex for about three weeks due to my wife being away. The penis also hurts a little when I pull my foreskin back. I am 52 and as far as I know healthy