Allergies to anything he is coming in contact with? Have you tried washing bedding in a sensitive skin detergent? Maybe the floor cleaner has a new smell/flavor. Sometimes my little one likes to chew his paws when we come in from outside.
I usually wash his paws, then use a hotspot spray and put on felt booties. I find that they get used to apple bitter and put their paws in their mouth more than without. I hope you find out what's bugging your little man.