Welcome to HealthcareMagic forum.
I would appreciate if you can provide some more details about this lump.
- The size of the lump
- Is it increasing or reducing in size since it was noticed a month ago
- Is there any skin changes over the lump compared to the normal skin?
As there are no associated symptoms and your niece is comfortable, I do not foresee any serious pathology. It is also unlikely to be related to the fall. It could be a normal protrusion of skull, enlarged lymph node
or a developmental cyst
. A direct examination of the lump will definitely help in understanding the true nature of this lump.
The bottom line is I do not find any reason to concern. This is most likely a harmless situation which needs no further treatment.
Hope this helps.