Get a paranasal xray to rule out sinusitis,see ENT doctor for ruling out Deviated nasal septum ,or nasal polyps and other local conditions ,till such time u can use a nasal spray DOUNASE ,two puffs in each nostril ,take protein and
vitamin c rich diet , avoid cold drinks ,smoking ,dust, use a suitable mask while in crowds ,also avoid dust,strong perfumes, agarbatti and mosquito coil smoke which may be causing allergic rhinitis