MacOS Update issue

I tried to update OS on my MacPro with Sierra and the installation stopped for a long time at the end of the installation. So I had no choice but to shut off the Mac with power button. I tried to reinstall the OS with recovery mode but again it failed. Now, I am not able to start my Mac. Please help.

Did your Mac startup in Recovery Mode? If it did then use Disk Utility > First Aid to repair the hard drive.

If not, then try an SMC reset: