If you have developed a single cold sore on your lip at this stage, the chances are you have had HSV1 for a considerable period of time, probably since your
youth. The
stress you are presently under has probably contributed to the outbreak.
Of course if you aren't familiar with cold sores, this may not be one.
In this situation, try to get to 16 weeks before testing. A positive HSV1 result I would suggest indicates a prior infection.