If your RRSP contribution was not claimed or reported on your 2016 tax return, you will have to make an adjustment to that tax return. CRA requires that you report all RRSP Contributions made from Mar-Dec of 2016 and the first 60 days of 2017 on the 2016 tax return.
You can make an adjustment through your CRA My Account or mail a paper copy to your tax services office.
Your overcontributions will be added to the return and carried forward to deduct when the room is available.
https://turbotax.intuit.ca/tips/how-to-resolve-rrsp-over-contributions-5540
