It's probably a Bartholin Gland Cyst. I have had one. Go to the gyno. If it gets too big they might want to remove it. Mine went away on it's own but my grandmother had one that was so large they had to remove it. It's nothing serious, just a blocked gland.
Well I did have a child, but it was c-section, and I never terminated a pregnancy, but I actually noticed this on the exact same side, exact same spot on me as well. My first thought was some kind of cancer, but I don't think that could be possible... its not like its a breast lump or something. I am not entirely sure , but if you find anything out, please send me a message and let me know. Thanks