Cold sore in mouth a day after possibly accidentally using hep c girls glass would that be coincidental?

Hep C is not herpes: Hepatitis c and herpes simplex (cold sore) are different viruses and are not related. Hepatitis is most commonly w/o any symptoms although it can be seen with abdominal pain, yellowing of skin and eyes, discoloration of stool and urine. It takes more than one day for either hepatitis c or herpes to develop. Most likely you have been exposed to herpes previously and it just came out at this point.

Cold sore contagious: . Cold sores, also called a fever blister or herpes simplex type 1, are groups of painful, fluid-filled blisters. Unlike canker sores, cold sores are caused by a virus and are extremely contagious. Also, cold sores typically appear outside the mouth -- usually under the nose, around the lips, or under the chin, while canker sores occur inside the mouth.