HELP ! Add Child To Submitted PR application INLAND APPLICATION

[masm]

Hi, First of, Me My Son and My Common law of 5 years came to Canada in April 2015. my Common law is Canadian Citizen by decent. I applied for my sons Citizenship as soon as we arrived and that has been declined as my common law was not born in Canada and to allow citizenship by decent is now only allowed to one generation. I have also submitted my PR application in October 2015 My common law being my sponsor.
I am now wondering how I go about putting my son on my already submitted PR application since he has been refused citizenship.

any comment will be appreciated!

Thankyou