as per the information provided by you the white patches you can see on yor gums are nothing but dead tissue which is going to be replaced soon by healthy tissue by body in few days.
feeling such pain is acceptable in some cases for first 36 hours of the surgical procedure and the pain should start to subside then.
if not then you should see your dentist
and let him guide you further.
if there is a dry socket
then the dentist would do the dressings and the pain will subside eventually.