Why is Nicholas so frustrated when the doorbell rings the night Paige returns from being gone for three months?

Max has his first cold and Nicholas is miserable watching his son struggle with the stuffy nose. Nicholas spends the entire day carrying the baby around, attempting to keep him comfortable. Now it is late, and Nicholas is sitting on the couch watching the evening news with Max in his arms. The doorbell rings just as Max has fallen asleep. Nicholas is angry because the baby is awake again and Nicholas has surgery in the morning.