Cat has bad habbit....?

I have a 6 month old cat who likes to suck and lick on the bottom of his front paws. He does it when he's sitting with me and when I go to bed. It's really annoying at night because he insists on laying by my face or head and purring and sucking loudly. I know it's probably like a toddler with a pacifier, but I don't know how to make him stop. Any ideas?