hello and welcome to health care magic, You need to understand that sinustis is essentially the problem of the sinuses beside the nose and although they can be associated with nose block; they usually present with headache. So essentially when we say sinusitis it means headache due to sinusitis though they may have other features. You seem to be having a deviated nasal septum which could cause this block and also allergic rhinitis which can explain the allergy. In any case you must get a CT PNS and allergy testing done and get back to me or any ENT with the reports regards Dr Sriram Nathan