Yellow sputum in the nasal cavity in the morning is most commonly caused by septic infection of the nasopharynx or pharynx due to infection of the upper respiratory tract, mostly accompanied by nasal congestion, runny nose and sore throat, which requires antibiotics for treatment. For nasal infections, the more commonly used antibiotics are penicillins or cephalosporins, which can be treated with amoxicillin clavulanic acid potassium or cefadroxil. In addition, you need to take cough and phlegm relieving drugs, such as aminoglutethimide oral solution or pulmonary cough combination. If accompanied by headache, dizziness and weakness, it is likely that sinusitis is the cause of the yellow phlegm in the nose in the morning, when the first step is to go for a CT examination of the sinuses to confirm the presence of sinusitis. If you do have sinusitis, in addition to treatment with the above antibiotics, you also need to perform nasal cleansing, which needs to be done by a doctor at an ENT department.