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It would have to go back to NZ for service. It is unlikely you can resolve any problems once they have come to light but if this is a recent event and it still works, you can put it in front of a low heat hair dryer for a while.
If you have Apple Care + this would be considered as one incident. But that feature is only available in the country which services the warranty.
Question: my 5s dropped in water and won’t turn on, What do I do?