I get a similar sounding bump (very painful) every once in a while in the same area. I think mine is a small cyst type thing (technical term) and it usually goes away on its own although it takes some time. I did show my gynecologist and she said a hot compress would help ease the pain. Mine show up for no reason either. I luckily haven't had one in about a year. Probably going to your gynecologist is the best bet for an answer although there may not be a treatment other than time to let it heal.

That must have been some wind that blew you off your bike!!!