I am suffering from severe cold symptoms, a runny nose, and sinusitis. I am also experiencing a very intense headache, and the pain is so severe that I am unable to properly open my right eye. Could you please suggest the possible cause, whether this could be serious, and what treatment or immediate medical attention may be required?

Your symptoms are highly concerning. While sinusitis causes facial pressure, an intense headache combined with the inability to open your right eye suggests a severe complication like orbital cellulitis (infection around the eye) or cavernous sinus thrombosis. These are potentially vision- or life-threatening medical emergencies. Please go to the nearest Emergency Room immediately. Do not rely on over-the-counter medicines or wait for a clinic appointment. You require urgent medical evaluation, likely including a CT scan and intravenous antibiotics, to prevent permanent damage.