I'm not sure there's one right answer to this. If you blow, blow gently into a tissue or handkerchief. Don't blow so hard it hurts. Sniffing isn't the most pleasant sounding or feeling action.
Even better than either of those options, though, is to prevent the nasal stuffiness in the first place. You don't say if you have allergies that are causing this symptom, but if you do, the best approach to preventing allergy symptoms is to avoid your triggers and to take your allergy medicine.
Common allergy triggers include pollen, dust, furry/feathered animal dander, mold, and insect droppings. You'll get the most bang for your buck by eliminating those things, as much as possible, from your bedroom, since you spend so many hours sleeping.
Allergy treatments can vary. There are oral antihistamines, as well as nasal ones. There are also medicines such as Singulair and nasal steroids that can treat allergy symptoms. Talk to your doctor to find out the best treatment approach for you.
To your health,