What Causes Discharge Of Yellow Liquid From Nose On Bending The Head?

Yellow colour liquid coming out from my nose but its its not regularly when ever my head hit slightly some where or some one hits on my head suddenly sometimes when I bent my head down this started almost 6 years I don t know untill now if it s a serious problem and this liquid where like sticky and after stop this my nose get try like powder inside please tell me if this is serious or jest a alergic problem