Air con seems to be to dry for 8 mth baby, is it better to put humidifier in the room? will it help baby with sensitive nose?

Humidify: Central air runs through the same forced air ducts as winter heat does. It's very dry, even when there is a central humidifier attached. In-window air conditioners also tend to dry the air especially if the house is tight & well insulated. So yes a good humidifier would be helpful. Saline nasal spray before and after sleep is also very effective. Use the ones made for babies.