My 4 month old son always suck his hands fingers ,even after feeding him. I m afraid of that later on he will suck his thumb? I dont know how to deal with it

Firstly divert him when he is on the way to suck fingers. Hand gloves for kids are available in any baby shop. Use those. Change them day by day .don't let him suck his fingers they might push the tooth forward or may cause stomach upset because kids crawl on floor and their hands might be dirty