J.Y.
I recently had a ruptured ovarian cyst. And like you, it was extremely painful!! The doctor said it is one of the most painful experiences you will ever have. Personally, the enema CT scan they did in the ER was (if you can believe it!!) more painful, or at least it caused the ruptured cyst to be even more painful! Luckily they had already given me morphine, unfortunately they had to give me more after that procedure (which they did to rule out appendicitis, since it was on my right side).
Neither one of my docs were worried either. And from the research I did on my own, having cyst is normal part of life for a woman and though them rupturing is not as common. They also found another cyst on my left ovary, but again, they were not worried, said it would go away on its own. I am having my ob/gyn doc pay more close attention, since female problems run in my family, include PCOD.
I believe my pain lingered for several days afterward, kept taking Ibuprofen until it subsided. If I remember right from the research I did, the lingering pain is from all the crud that the cyst released into your abdomen when it ruptured. It takes time for you body to reabsorb all that and then expel it. I don't remember getting headaches though.