The cold virus, assuming this was the original problem will be long gone by now, not that you could have done anything to treat it anyway.
There are I suppose 2 possible causes of your symptoms, the first is that though the infection has gone, you have lost membrane stability in the respiratory mucosa of your upper airways, producing a post viral hyper-reactivity. This is more common in the lower airways, where the equivalent effect would be to cause chronic cough.
The other possibility is that your problem was always allergic, rather than infective and you are still being exposed to the allergen.
The good news is that the same management would work for both problems, inhaled nasal steroids. The mildest of these can be bought over the counter as Beconase. Drugs like Nasonex are more effective, but are prescription only.
GP for more years than I care to remember