It sounds like you could have had a cyst that no longer appears on ultrasound that ruptured. Many cysts become fluid filled and disperse the fluid upon rupture, which then has to be reabsorbed. That causes pain and swelling/distention until it resolves itself. How long depends on how much needs to be reabsorbed but it could be longer than you would like (weeks). Other than checking for infection, which I assume the doctor would have done, and treating for the pain, you had good results from that test.