There are several reasons why dogs may lick their paws:
Cleaning themselves: Dogs may lick their paws to clean dirt or bacteria from their feet as a form of self-protection Knee reaction.
Pain or discomfort: When your dog is in pain or discomfort, licking his or her paws may provide some relief, as The same way humans rub their heads.
Distraction: Sometimes dogs are distracted by external stimuli, and licking their paws can become a habitual response.