Welcome to LQ.
The default ns2 build location is /home/<name>/<ns2>/ . ( Not the Desktop/.)
No reason to use 'sudo' for any ns2 commands. ( Unless you are looking for troubles.)
* Exceptions : 'sudo make install' , 'sudo cp ns-new-name /usr/local/bin/'.
Your issues : Nothing in your post is showing any errors. Just the normal things.