Paragon Migrate OS to SSD 5.0 Safety

I am migrating my original 1 tb WD HDD to a SANdisk 1 tb drive via USB to SATA cable. During the process I get a warning that certain files that are in use have to be closed and the laptop needs to be rebooted to finalize this.
There was another option to choose to close the files and try again which I selected. If that does not work I might have to reboot.
My problem is that I am worried that once the LT is rebooted changes will be made to the original OS and once shutdown again it may not boot with the original HDD if the new SSD drive does not work?
Is it safe to allow the reboot? Will there be any changes made to the original drive. I do certain remote work 2X daily that I cannot afford to miss, so my PC cannot bein a non working state!
Any help / suggestions would be greatly appreciated!
Thank you