Hi, My 9 Year Old Daughter Has A Sudden Bump

Hi, my 9 year old daughter has a sudden bump on her forehead from no injury. She brought it to my attention early this morning and at the time it looked like a mozzy bite. She spent most of the day playing and expressed a little discomfort throughtout the day, but I asked her to not touch it and leave it alone. At around 5.30 this evening she started complaining again. This time, it was red and grew in size. It looks like a small egg on her forehead.
What could this be? Do I need to seek medical advise??