What Is The Swelling On The Vaginal Lip That Eventually Subsided?

Hi, so this morning I woke up with my right inner vaginal lip inflamed (not like a rash, it was swollen into the size of a grape) it didn't burn, itch, look like a pimple, and was kind of squishy. The night before I masturbated twice and for the past week I was having some vaginal itching. I've had the same sex partner for the past 2 months. I was afraid this was herpes but, after checking online the symptoms didn't quite look similar nor was the inflammation sore, burning, or itchy. I took a shower and put on my panties, about two hours later I went to the restroom to check it and it was completely back to normal. What could this have possibly been? Please please please help. Thank you.