I am a tidge late in replying to this post. I do hope your daughter is well. My daughter had the same problem. Turned out, she had an allergy to the material the earrings were made from. It got infected, turned purple and blue and yep, a blood clot formed. I took her to the er. I felt silly afterwards because it was something so simple. At the time, it did not look good, so simple was not in my vocabulary. If you ever get concerned, afraid, etc about anything health related and cannot get to the doctor right away, the er will not turn you away because it is less of an emergency. I say better be safe than sorry. :)) Your princess will be fine. Those pesky earrings!!
Go to the ER just incase but it sounds like it could be a bit of bruising.
Call the nurse hotline and see what they say. I dont know I got my daughter ears done by her doctor but I would call the nurse hotline