Parents have asked: "How do I encourage my baby to open his mouth and take a mouthful of baby cereal? He doesn't seem interested."
It may be that your little one is not ready to wean yet. If he's growing and developing healthily and taking enough milk then maybe try again in about a week.
Watch out for the signs that he's ready to wean such as taking an interest in your food, being able to hold his head up straight without needing support and seeming less satisfied with milk feeds alone.
If he's already weaning then maybe try a different cereal, such as Creamy Oat Porridge or fruit purees. He may just need a bit of time to get used to new tastes.