Then the owner REALLY needs to reassess their training techniques, and avoid situations that make the puppy feel the need to bite. If the owner is using compulsion based training, they need to stop, and start working with a good, positive based trainer, and learn how to set up both the puppy and themselves for success.
As for how long it will take for the puppy to "forgive and forget", well, that depends on a number of things, including, but not limited to, the puppy's innate temperament and confidence, their developmental stage, and how much of a bond they already have with the owner.
The owner also needs to realize that puppies, especially baby puppies, explore the world with their mouth (so do human babies, for that matter....), and when you add in possible teething pain, then you might just have a landshark on your hands for a while.