Same situation I am waiting for final visaDefinitely, he can come to Canada, Even, I am in the same situation, I have already missed my January 2019 intake. waiting for final VISA result to come. Once, I got the approval will ask my college to provide September 219 intake admission letter and I can use this VISA while travelling Canada in the month of August 2019.
You nephew can come to Canada just 1 month before his intake start date. No, need to inform any immigration people in Delhi.