What Causes Reddish Sores At The Base Of The Penis?

I am embarrassed to say it, but my girlfriend and I tried speed for the first time and ended up having sex for 12 hours. I was having erectile issues so I used a cockring off and on. I felt discomfort(during sex) and eventually(shortly after sex) pain around the base of my penis but saw no visible blister or rash. It has been about 3 days and now I have a cluster of reddish sores at the base.