Nobody will stop you from leaving Canada. You might just have a problem coming back.
These are your options:
You could wait for your PR card to arrive in the mail.
You could go to India but have someone mail you the PR card when it arrives.
You could apply for a PR travel document at the Canadian embassy in India.
If you still have a valid multiple entry visa in your passport, you could show that to the airline to board the plane but when you arrive at immigration in Canada, you should show your landing papers and disclose that you are a PR.