Thank you for the question.
From what you are describing this might be one of three things:
1. A deep vulvar abscess
- it does not have to come to a head to be an infection
2. A hernia
- this is a common location in women and would present very similar to how you are describing it
3. A vulvar varicosity - you have veins in the labia that most commonly get swollen during pregnancy
, but this could happen at other times, especially if you have had kids before.
I hope that this helps and good luck.