If not under warranty, you could try to fix it yourself if the damage is minor. Maybe some glue or tape could do the trick. But for major damages, it might be best to look for a professional repair service or consider buying a new one.
To be honest, I don't have the exact count of how many Nana manga there are. It's best to refer to official manga sources or dedicated manga communities where you can get a clear and up-to-date number.