Your puppy has associated you with the punishment you delivered for her nipping. Now she trembles in fear or avoids you altogether whenever you approach because she’s anticipating another swat on the nose. This can happen if a punishment is too intense (your puppy may be very sensitive, and the swat was too harsh for her) or if she has not already learned to associate your hands with good things.
A puppy should be taught right away that being handled by the owner is always lovely—hands give treats, tickles, toys, and gentle touch. The same rule applies for the puppy coming to the owner. Each time the puppy comes to the owner, good things should happen. With a foundation like this—which can take as little as a few days or as long as a few weeks, depending on the puppy’s temperament—she will be able to make the connection between her behavior and the punishment should she receive a mild swat on the nose.
Your puppy can learn to trust you again but you need to be very patient and tender with her. Give her treats frequently. If she’s too wary to come close to you at first, sit on the floor and toss them near her. As she relaxes, draw her nearer to you, but don’t reach for her. Take your time, and allow her to come to you. Use tiny pieces of a special treat food, such as cheese or chicken. When you see your puppy settling down for a nap, sit by her, remaining quiet and calm. Over time, she will become more comfortable with you approaching and sitting with her. The next step is to touch her—and eventually, you should be able to hold her in your lap and stroke her while she sleeps. The most valuable advice we can offer is that you should never strike this dog again. She is unlikely to be able to withstand or learn from any harsh physical punishment.
Puppies bite for many reasons. Your puppy may have been feeling playful, feisty, or fearful. Without knowing many more details I can’t surmise as to why your puppy nipped at you—but it is important to let your puppy know you don’t want her to bite you. Should it happen again, we suggest that you yelp loudly and quickly walk away from her. If it’s safe to do so, you can leave the room briefly. If she is apt to get into trouble alone, then place her in her crate, with the door closed, for two to three minutes. Then, bring her back out and resume your activities. She’ll get the idea that nipping at you will cause you to go away. Most puppies prefer to be with people, and will do whatever is necessary to stay in their good graces.