Are you certain it's a cold and not allergies?

I'm not sure how old this child is, but my daughter, who is 8, has a runny nose from September until at least Jan. Some days it's gross and some days it's clear, but we can never seem to get it to go away.

It may just be seasonal allergies and for that there's really nothing you can do just deal with it.

I keep a bib on my little ones that have runny noses. That way I can wipe quick and move on. When it gets too yucky I change to a new one.