If it has lasted for a long time, it is either allergies or a sinus infection. First, take a decongestant to stop the symptoms. Then try an allergy medicine like Benadryl. If that does not cure it, see a doctor for a possible sinus infection.
Runny nose can be treated in many ways. You can apply herbal ointments on your neck
region and on your nose. This can stop running nose. You can take a warm water bath.
That sounds like seasonal allergies, especially if you aren't having any other symptoms like fever, coughing, or fatigue. You can try something like Zyrtec or Claritin, and see your doctor to rule out any other problems.