Thank you for your query,
The bump is due to formation of hematoma
layers out side the skull.
As the became active nothing to worry.
But observe for her sensorium, for vomitings, bleeding from ear, nose and drowsiness
and decreased movements and if you find any abnormality take her to emergency.
If there is no problem, consult your Pediatrician
for a examination to find any abnormal signs.
Hope I have answered your query.