The first time someone used this word when talking with me they also pointed to their cheek. I immediately went into language survival mode, scrambling for context and meaning. "Nose? I have something in my nose? No? An eyelash? Yeah, I know it's jiemao, but what are pointing at, exactly?" The only thing that's changed is that I don't ask questions anymore; I know the meaning. Students will still point and say "dou."
Chinese people are amazing at making your business their own; they are looking out for you and trying to help. When I realized that the meaning of "dou" was "pimple," however, I wondered about the nature of their concern. It's common to hear this from my students, the only prerequisite being, well, a pimple. I have heard this so much that I'm rather accustomed to it now.
The other day one of my students asked me how to say "dou" in English. I said that there were several ways: "Pimple," "zit," "boil," well...you get the idea. I thought about it for a moment and then explained something to the student (something that probably saved the student from an awkward moment of my cross-cultural rage). I said that there were indeed several ways to say "dou," but that I preferred to hear "dou" because the word was firmly within a Chinese context. I don't know how often I would be able to hear, "You have a zit on your face," before I would just snap. "You have a dou" sounds so much nicer, don't you think? Actually, after being immersed in this culture, it sounds almost NORMAL.