I had an experiece like that when I was pregnant with both of my children mine were a little bigger than a ping pong ball, I could not wear panties for long peroids of time but what I did notice was lace boyshort panties did not bother me. When I went to see my doctor when it was bad enough she said it was an infection. She was not sure what type it was but is was not sex related since I was not having sex due to my husband being overseas, I guess because she was thinking it was pregnancy related since it never happened before or after the babies but go see a doctor for an antibiotic, you will be fine.
It could be a Bartholin's cyst. These can be acute or chronic. If it hurts or seems hot it could be infected and needs attention. See a gynecologist.
Hi there!
It could be your lymph node that is inflamed. Give yourself a rest and find out if there is any problem in your body which is near to it. Just don't touch it all over again. Give yourself some healthy food and enough vitamins to counteract any infection. It may go away after 2-3days. *Stay Healthy* ^_^