What Causes Dripping Of Clear Liquid Through Nose?

My left nostril occasionally drips a clear liquid...sometimes when I m eating. I m 77, good health, no prescribed meds,20 lbs overweight, workout, bike, swim. I occasionally sneeze about 13 times in a row. No cold and no alergies (maybe newsprint) that I know of. Do I have a tumor in my sinus cavity that s going to do me in??