I have an Itel based iMac on which I created a Wifi network using Airport. My iPhone5 uses the Wifi on my iMac and still works.My problem is that I can't remember the Wifi password and it is not in my Keychain.
Read the router's user manual on how to change your password.
If you are going to select another password, make sure it's one that you will NEVER forget AND no one else can figure it out. Print it out & keep in a safe place. A place that ONLY you know about AND never forget.