red marks on tip of penis

[concerned in california]

About two weeks ago I was experiencing a really sore throat with non-stop coughing so I quit smoking thinking I just had a cold and the tobacco was exacerbating the sore throat. After about a week my sore throat went away and I haven't smoked since.
After I was feeling better my girlfried and I had unprotected oral sex. Days after she and her close friend came down with something that later turned out to be strep throat. Since then I have also found small red marks on the tip of my penis that were never there before. They have been there for two days now and I only just found out that she tested positive for strep throat. At first I thought I might have given her strep but now I am wondering if the red marks on my penis may have been caused by strep or possibly something else. The marks are very small and there are about six of them all around the tip. Is it possible for strep throat to manifest as an std or should I make an appointment with my doctor as soon as possible?