A saline (salt) water nasal spray can be used to help you unstuff your nose and help keep your nose clear. Even if it doesn't fix your sinuses completely, it can help loosen the pressure enough to get you to sleep. You will need water, salt, and a small spray bottle.  The spray bottle should be a one to two ounce bottle. You can use sea salt or table salt.  Boil eight ounces of water and allow it to cool until it is very warm. Add ¼ teaspoon of salt to the eight ounces of water. Mix well. Add ½ teaspoon of baking soda.  The baking soda will help lessen the sting of a very sore nose. Pour into a spray bottle. Spray one or two squirts into each nostril as needed. Repeat this only four to five times a day. One common cause of stuffy nose is allergies. If these are causing you to have a stuffy nose, especially at bedtime, try taking an antihistamine before bed. It may also have the added bonus of causing you to get sleepy, which will also help you sleep better even if your nose is still stuffy. Many antihistamines cause drowsiness. Look for a non-drowsy antihistamine if you need to take it during the day. Do not drive or operate heavy machinery until you know how the antihistamine affects you. If your stuffy nose is caused by allergies, you may want to to try a nasal steroid spray to reduce inflammation. When you use these sprays you will experience quick relief, but you'll need to use the spray continuously to get the full benefit.  Most nasal steroid sprays need a prescription, but there are current two available over-the-counter — Flonase and Nasacort. If you have seasonal allergies, start using a nasal steroid spray at the beginning of the season to lessen your symptoms.  When spraying the spray into your nostril, you'll want to point it toward the outer-wall of the nostril, not straight up or toward the inner-wall (septum).  Side effects may include dryness or stinging, sneezing, and throat irritation. If you experience a headache and nosebleeds, call your doctor right away. While you are sleeping, prop up your entire upper body. This can help drain your sinuses and keep them from getting stuffy.  If you can, put some blocks under the head of the bed to raise the whole bed. If you can't find any way to clear your sinuses, this will also help you sleep. Keeping your head up will ease sinus congestion to help you sleep. To cut down on stuffiness due to dry air, keep your bedroom humidified. To do this, use either a humidifier or keep a bowl of water near your head. The water will evaporate during the night and help keep your sinuses damp. Dry sinuses make stuffy noses worse. Keeping the air humid in the area where you sleep will help you sleep better with a stuffy nose.

Summary:
Make or purchase a saline spray. Take an antihistamine. Try a nasal steroid spray if you have allergies. Prop up your body. Use a humidifier.