dd1 had this after a vaginal vacuum extraction. poor little darlings, it must be really sore i always though. i was told it was a hematoma (bruise). there was also a little scab in the middle of hers from where they put in the monitoring device. i cant remember exactly how long it lasted but i do remember it was there for a fair while after they said it would go away. oh, and not there was not depression after it finally went away.