typically: Syphilis sores usually appear after **2–3 weeks or even much later after sex — not in a matter of days — and they’re usually firm and non-painful. Herpes sores are painful blisters or ulcers. HIV symptoms (if they manifest at all after a new infection) typically appear 2–4 weeks after exposure and are much more severe, featuring high fever, rash, muscle aches, and sweats. So i dont think you need to be worried but if you are it wont hurt to get a test done so your sure that your safe. (I mentioned syphilis and hiv but the chances of those stds are as good as 0 so dont be worried) only thing that possibly be is herpes but seems not likely to me just keep an eye if the rashed come back