What Causes Sore Spot On Foreskin?

Hello Doctor, I have a spot or something under the foreward end of my foreskin. It can be rather sore, especially when adjusting my foreskin. Sometimes, when I pee, it aggravates the spot causing soreness. At the moment it is itching. I have had the complaint for about 3 weeks. It is rather red. I have tried E45 cream to soften it, without success, so I smothered the area with Vaseline which has altered the colour of my glans, it looks anaemic, but still I am sore. The problem is aggravated by my rather tight foreskin, the likes of which is quite easily drawn back when my penis is flaccid, but with a good erection it hurts a bit. With the skin pulled back, the spot obviously comes back with it and is stretched out which worsens the problem. I am 66 and amongst other things, I have type 2 diabetes. Could the Metformin be giving me the problems? My wife who is 70 still suffers from the after effects of shingles in her groin which she had many years ago. This makes intercourse difficult and uncomfortable for her, so we restrict it to about once a month. However, I still get a bit fruity and so she obliges me with a handjob about twice a week. This did not cause a problem until the spot appeared. By the time that I have ejaculated, my penis looks like it has been in a fight!! and also feels like it. I have no idea why this is. Can you help me please? Brian.