It could mean any of several things. You could have an allergy. You could have emphysema. You could have lung cancer. It could mean you have a cold. If this problem has been going on for an extended period of time or if you are coughing up blood, see your doctor for a proper diagnosis. It is more than likely something that can be easily treated but until you see your physician, you will not know for sure. Better safe than sorry.
If it is a dry cough I think I would be more concerned. Do you have allergies, or has the climate changed recently. If it is a productive cough you may have the beginning of a virus or cold. If it does not get worse, I would not worry too much. Ah do you smoke?
The cough can be due to many reasons. There are two types of cough. The productive or non productive cough. Both have different treatment. You have not mentioned which type of cough you are having. If you are having cough due to allergy, this can not be treated until removal of allergen. Visit a doctor for differential diagnosis.