Ear problems such as a blocked feeling or pain can have local causes – related to the ear itself – or come from nearby, connected structures: the jaw joint, gums, teeth, larynx, pharynx, tongue and tonsils. A blocked ear may be due to tooth pain caused by the teeth moving, as the two areas are supplied by the same nerve. Still, this isn't typical, so more common causes such as an ear infection, problems with the Eustachian tube and so on should be looked for and ruled out. It's also possible that getting braces simply coincided with another, unrelated problem, so see an ENT specialist.
This answer is for general information. Your own case needs an examination by an orthodontist.