I'm on here because I feel weird asking anyone this.

A few days ago, I got a bj from a gf. She said she had a cold sore but it was pretty much gone. Two days later I notice a sore on my dick. Idk how to tell her, I feel like asking if she has been with anyone while we were dating, how would you go about phrasing that? Does this really require a doctor? Do I need to tell future plates this if it goes away?

I'm not an advocate for condoms, I like marking my territory. But don't be stupid and hook up if you think she may have cold sores.