Thank you for your replies. I have withdrawn my PGWP application using the web form.I don't know if @profiler knows a better way, but you can withdraw using this link:
http://www.cic.gc.ca/english/helpcentre/answer.asp?qnum=741&top=23
I know your study permit allows you to work, but from the time you finished your degree, I'm not fully sure you still can use your study permit to work... so I would keep quiet the fact that you are currently working.
Regarding working on study permit, I read this "http://www.cic.gc.ca/english/helpcentre/answer.asp?qnum=1181&top=15" and it says that you are eligible to work while waiting for your PGWP.
And also, I started working on the day I received my landing interview request, so essentially, I couldn't inform before that.
Even now, should I keep mum about working?
If not, should I fill out the same web form to let CIC know about my employment?
Please advice.
Thanks.