You can try to pick ‘root – Drop to root shell prompt‘ from Recovery Menu
sudo fdisk -l
#should give something like /dev/sda3 on / type ext4 (rw,errors=remount-ro)
sudo fsck -f /dev/sdaX
sudo mount /dev/sdaX / -o remount,rw
Now you got root access to partition and can try to fix it from there.