You might need a chest x-ray, but "chronic cough
" (over ~6 weeks) is most often from one or more of: a) asthma
, b) post-nasal drip, and c) acid reflux
If the cough began after a "cold" or similar symptoms, its probably one of the first two. Cough suppressants don't work very well, and if your cough persists, see your doc, especially if you smoke. Most chronic cough goes away or can be treated.