After reading, I see that I need the 24 words to be able to update it?
If the update works without an issue, no.
It may only be necessary to reset your device if the update fails (e.g. got stuck).
Edit: And if you are updating to 1.3, like Lucius already mentioned.
The reason is that I am not sure yet where are the 24 words :/
Are you still able to access your wallet? What kind of an error message did you get? Or is it stuck in a loop?
If you still can access your coins, i would suggest you do send them to another (temporary) wallet until you have initialised your nano s again.
Or if you don't want to do that, you could try to restore some 24-word-seeds you can find around your place in an offline environment to check whether they match your nano s seed/addresses.