Another way that the body tries to react to an infection is to produce mucus. This is intended to drive out the virus and at the same time to help prevent more unwanted foreign bodies from getting in! Thus it is common to produce a lot of mucus in the throat and in the nose, which can make it difficult to breathe (especially through the nasal canal which is much more narrow).
You may find that it’s hard to get comfortable and to sleep because of the blocked nose. The solution therefore is to try using something in order to break up the mucus and the congestion. You can do this my inhaling a number of essential oils, or alternatively by inhaling steam. To do the latter, hang your head over a bowl and fill it with boiling hot water. Then drape a towel over your head and over the bowel and this should then trap the hot air in with you so that you have no choice but to breathe it in.