Can Urine Irritation Cause Sores In Vagina?

I have had two single genital sores in my life time, about 3-4 years apart. One occured before I had ever had intercourse and the second just recently. Since I was a child I have terrible had oral canker sores, when I was young up to 10 at once. The two genital sores look similar to a canker sore. They occur at times when I had not bathed in two or three days. Could this be due to urine irritation? I don't see how it could be the result of an STD if the first instance occured before I had sex.