hello and welcome to HCM forum,
thank you for writing in,
first of all,i would like to inform you that yes your are right,the pain is due to sinusitis
you have not mentioned anything about the nature of pain ,i assume pain is present only on one side and is generalized, it might be dull but continuous in nature. also, pain is associated with nasal congestion
i would recommend you to visit an ENT specialist
, a week long course of antibiotics and anti allergics are some of the medications that will be prescribed .
whether required on you or not depends and will be decided by your doctor,therefore meet your doctor soon,
i wish you good health.