itchy stingy .. help

L
I've got this little sore on the inside of the outer of one of my vagina lips .. It stings and sort of itches. I took a look at it and it kind of looks like a small ulser like you'd have in your mouth .. I haven't had sex for a few weeks and shaved almost a week ago and it's just come up in the last few days ... Does anyone know what it could be ??