This might be a permission issue on the current directory you were working on.
And the file you created is not your ownership since you send a sudo command on it.

Try to check your current directory's permission.

If you don't have permission to it you can have

$ sudo chmod -R 755 Your_Directory/

or

change the ownership of that directory.

$ sudo chown -R user Your_Directory/

Next time you create a file just type

$ emacs "Your File in Here"