Hmm, I don't know. Could anything have gotten in your nose (I know it sounds crazy, but you never know)? Usually when you have a sinus infection, in my experience anyways, the mucus is thin and has a yellor or green color to it. If the smell persists I would definitely see a doctor, it could be a sinus infection and you may need antibiotics. Have you tried rinsing with something like a netipot? You can get them at walmart and it looks like a little pot. You just fill it with water and the saline pack it comes with and it cleans out your nose and sinus. It would be something to look into, but you should probably see a doctor if there's a foul smell.
Hello and hope you are doing well.
It could be a nasal polyp, this can be mobile and cause nasal obstruction. The nasal block could also be due to a sinus infection, a cold or a chronic allergy. It could also be due to a deviated nasal septum. Sinus infection causes blockage of flow especially when a person lies down. The blockade is affected by the side to which the person turns also. You will need to consult your primary care physician for proper assessment. In the meantime practice good breathing exercises, humidify your room and do steam inhalations.
Hope this helped and do keep us posted.