I received oral sex from a close female friend last night. It was our first time together. She used a little too much teeth but we finished and she swallowed. Later in the night, I went to the bathroom and noticed I had a little bit of what seemed to be a cut on the base of my penis beneath my head. Its pretty much tiny, maybe a couple millimeters but it was easy to notice and I'm a little worried. After looking at it carefully I noticed that it doesn't seem to be an open wound, rather it looks more like a tiny blood vessel thats inflamed/irritated but I can't be sure. Now, today, it looks the same except its dryed up a little bit, what was red is now turning brown sort of like a scab. But the skin is perfectly smooth, its almost as if its underneath my skin. Thats why I think it is just an inflamed blood vessel. I don't THINK it was ever an open wound but I can't be positive. My question is this: is there any way that the sore on my penis could have led to any STD exchange between us? As soon as I noticed the sore, I took a shower and washed it carefully and none of what seemed to be blood washed off, which is also why I think its all an inflamed blood vessel underneath my skin. Has anyone ever experienced anything like this before? Am I at risk? Might sound kind of silly cause the cut is so small but I am sort of nervous.