Hello , the info u given is insufficient . Nasal blockage may generally occur due to nasal polyp . When we lying down all mucus get accumulate in the nasopharynx area n nasal polyp get enlarged due to accumulation of fluid that's y daily morning u nose get blocked n u can breathe through ur mouth .
If ur nasal blockage problem is long lasting then better to start taken Homoeopathic treatment .
Homoeopathy can cure all ur problems.
Health Tips
Daily steam inhalation 2-3 times a day especially before going to sleep .
Drink Luke warm water daily morning so that ur throat get cleared .
Start doing some pranayam n deep breathing exercises.