It seems like you might have a sinus infection, which is when your sinuses become swollen and filled with mucus. Yellow or green snot is a sign of infection. Additionally, a sore throat and difficulty smelling could indicate a problem with your sinuses. To help yourself feel better, try using a saline nasal rinse and drink plenty of water. If your symptoms worsen or do not improve, consult a ENT specialist, they can offer more assistance.