Four nivhts now. Whenever I lay down my head hurts. One side of my nose is completely blockef, no matter what I do. Pain getting worse. What is it?

?sinus. Could be a sinus problem; when your sinuses are blocked changes in position can cause pain like leaning over to tie your shoes. If your nose is blocked you might have obstrucion of your sinus which can lead to sinus infection. Sometimes sinus rinses like neti pots can help flush open your nose and sinuses as well, you can try sudafed if you don't have high blood pressure or any heart condition.
Allergy or Infection. It sure sounds like you should be seen by your physician. This is an acute illness and you may need treatment.