Dear all Please guide me?

First try to repair file system by live cd and use

fsck /dev/sda

or Try below...

sudo fdisk -l

sudo mount /dev/sdaX /mnt

sudo grub-install /dev/sda --root-directory=/mnt

You should be able to access your system in terminal mode (rescue mode)

login and type the following commands:

sudo grub-mkconfig #To generate the proper configuration files.

and then type:

sudo update-grub

this command should regenerate the grub menu with the right filesystem mountings and reboot after that.

if you don't succeed? try 

sudo update-grub2

to fix the error more accurately try to provide some in-depth logs.

Thanks.