thanks for asking the querry..
i think this could be a infected post aural (suppurative) Lymphadenitis
or a post aural mastoid abscess
....if you have a past history of ear discharge
then its probably a mastoid abscess, needs urgent surgical incision and drainage
and also you have headache, blurring of vision means it might be complicated and involving intracranial complication......so its better go urgently to nearby ENT surgeon because when there is a throbbing type of pain then there is possibility of pus, thanks, have a nice day..