My 4 year old has been having a stuffy nose and cough for over a month now can this be serious should i take him ti see his doctor?

Possibilities...: If he has a fever, then it could be a sinus infection. If he doesn't have a fever, it could be allergies. It could also be a lot of other things. Definitely should see a doc for this.

Effect on lifestyle?: If your kid is playing robustly, resting well at night and the symptoms bother u more than the kid, simple monitoring is ok. Reduce or eliminate exposures to known irritants, smoke/fumes/etc. & a trial of otc allergy med may be in order. If kid is dragging around, not up to playing with peers, appears worn out or otherwise down, a look over with his regular dr is in order.