I had unprotected sex a couple nights ago and recently i developed a cold sore like thing on my upper lip, i was just wondering if its nothing or not ?

Cold site and sex: It is unlikely to be related to your encounter. If you are unsure of what it could be, then it is off to the dermatologist you go. Hurry though, it will probably be gone before you get an appointment.

May be related: You may have been exposed to an std such as herpes simplex depending on what type of sex you engaged in. I recommend seeing a dermatologist while the lesion is present so you can get an accurate diagnosis and proper treatment asap.