Thanks for posting your query on healthcare magic
Since your daughter had injury
to the forehead against a hard surface( side of pool ) she has developed what is known as a haematoma
which is associated with swelling and bruising . The only thing to get worried is if she has a history of loss of consciousness
, giddiness , bleeding from Ear, nose or throat .If this history is not there , then mostly there is nothing to worry .The haematoma will subside in approximately 10 to 15 days .Still she needs to be examined by a neurosurgeon to rule out any fracture
or internal trauma .
I hope i have answered all your queries
In case of any further doubts feel free to post again