I did all you suggested and then tried the sudo echo again. All seemed okay but i stiil could not write on my hard drive even after i unmounted and mounted with Disk Utility. So i decided to restart my computer to see if it would work but it didnt.
I also tried the sudo echo command again but kept getting the permission denied message. Also, when i try the sudo less command again, I get a 'no such file or directory' message