The middle ear is connected to the nose by a tube known as the eustachian tube. If this tube is congested or blocked eg. from a cold or enlarged adenoid then you could end up with a sensation of a blocked ear.
If the blockage is significant then you may sometimes end up with fluid in the ear. This will cause a sense of blockage and even hearing loss in the ear. As a patient; it is not easy to determine if its just congestion or whether there is fluid.
The only way to tell if there is fluid is to see your ENT doctor and he/she will put in an auriscope to check the middle ear. They will need to assess the eustachian tubes by putting a tiny camera into your nose to see what's causing the problem.