Yes your warranty will be voided. You could take it to a care center but they won't update it if the update isn't available for your carrier. So I suggest you just wait for the notification from your phone then download the update
I believe Ravi is from India so he has a factory unlocked Phone.
NSU should not void the warranty as its an official tool provided by Nokia to unbrick the device.
He is talking about NSU Retail and not the Nokia Care Suite, if I understand correctly.
Feel free to flash it using NSU Retail.