The only way to reset the SSH password of NAO if you have forgotten it is to factory reset your robot.
You can find the steps of how to do it here : https://support.aldebaran.com/support/solutions/articles/80000963150-factory-reset-nao-how-to-perform-
By default, the SSH IDs of a NAO are :
user : nao
password : nao
You can also try this combination and see if it works.
Hope this helps !
How do I reset the SSH password to nao?
I haven't used the robot in 3 years, and forgot the password.