Hi Kali,
You are having allergic rhinitis, Try with nasal spray (such as Rhinocort aqua/Flixonase/Flomist), antihistamines (Cetrizine/
Fexofenadine), saline nasal drops (to keep the nose moist) and drink plenty of water. Remember there is no cure for allergic problems. PREVENTION IS THE BEST TREATMENT.
Do not sleep directly under the fan, everyday change the bed sheet before going to sleep, when ever you are exposed to just cover your nose with a clean handkerchief. Any doubts you are welcome.