Conceivably have you formerly been down with a runny nose? Peradventure did you get rid of the virus? Naturally you got over it! You can't cure a common cold itself, but your body generally develops resistance to any type of cold virus within several weeks. We call that cured by your very own immune system!
Adults have in the past had a lot of the cold infections. Parents have established resistance to the ones they have had. Therefore there are not quite as many runny nose viruses remaining for parents to acquire. That is why grownups just acquire a few runny noses per year whereas kids succumb to 10-12 colds annually.