Vitamin D and the antihistamine in Fexovor don't interact with each other, so taking your vitamin D dose tomorrow as planned is safe even though you took the cold tablet today.
Next Steps
You can continue your usual
vitamin D schedule without adding any extra gap between the two. If the cold symptoms last beyond a few days or you get fever or sinus pain, mention it to your doctor given your sinusitis history.
Health Tips
Stop the cold tablet and see a doctor if you notice unusual drowsiness, a fast heartbeat, or any allergic reaction like rash or swelling.