You will have to:
Boot from the installation medium (a USB? A CD?).
Open the terminal, and determine the partition on which your Linux system is hosted. Issue the command
sudo partedand then, when the prompt appears,type p. This diplays the disk partition table. Your partition is neither the swap nor an the extended partition (if you have it, you might not have one). The partition you are interested in is the one with the boot flag. Let us assume it is /dev/sda1. Quit
partedby menas of q, thenissue the command
sudo fsck /dev/sda1When done, give the command
sudo shutdown -h nowNow remove the USB stick, and you should be able to boot normally.