For A Couple Of Days I Had Two Ulcer Like

For a couple of days I had two ulcer like sores on my inner vaginal lips. These weren't preceded by raised sores or fluid filled blisters, and it wasn't accompanied with itching, swelling or other common genital herpes symptoms. I have never had a cold sore, and it was only those two ulcers, no where else. I have gotten canker sores often in the past. I wasn't able to get to the doctor to see them because they were gone in two days. Is there anything that may have caused these sores other than genital herpes?