You'll probably need to reset the password on your router.
If you haven't changed the settings then the router address is normally
http://192.168.0.1 (or
http://192.168.1.1).
Standard passwords vary on routers but it is often admin and admin (and if it is then change it ASAP otherwise no point in having any security). If you can't remember that then you need to reset the whole router to factory which is by pressing a small screwdriver into a little hole at the back of the router.
That said there may be a hack to get the password elsewhere but this is what I would do (and have done!).