I have followed the sample here
https://github.com/awslabs/aws-sdk-ios-samples/tree/master/CognitoYourUserPools-Sample
To integrate interactive cognito login
The perfect example to implement the ResetPassword when u create the user in Cognito Console.
But, Integrating this ResetPassword mechanism to your existing app is your responsibility.
https://github.com/davidtucker/CognitoSampleApplication/tree/article1/CognitoApplication