When a child has difficulty breathing it is usually due to the airways being narrow somewhere or the lungs not functioning properly. The cause may be, for example, an infection, asthma or that the child has had an object in the airways. Breathing difficulties can be very serious and you usually need to seek care right away for the child.
Nesting and sniffing are common. Often this is due to a cold, but it can also be due to allergies, sensitive mucous membranes, pregnancy or that you have used nasal spray for a long time. Often it goes away by itself but sometimes you need treatment.