It sounds like a Bartholin's duct cyst to me. They can vary from being quite small (but painful) to very large.
I had one the size of a marble approx 3 years ago, I treated it with hot bathes and when the pain was extreme I used a hot face washer (as hot as I could handle) and put it on the lump.
It relieved the pain for a short amount of time and slowly reduced the size of the lump.
I haven't had one since :D
If warm baths etc don't work, see your GP as it may need to be lanced.
Good luck :)
I have something like that too. And im scared. Mine is squishy and tender. And it hurts really bad. I have to sleep laying on my back and i cant m ove or it hurts really bad. I think im going to go to the doctor. But im embaressed and scared to tell anyone.
try sitz baths and hot packs to get it to drain...if not go to gynecologist