Well it depends on what kind of favouring it is. If he is doing stuff that abuses, offends or even disturbs you, you really do need to report it to someone higher up than him. but if it is just the occasional weird look and nide remark, how about sitting down and talking your problems out with him. Sounsd like the job is great so i think it is worth 5 mins of discussion and having a great job, rather than leaving it and possibly quiting.
But goodluck with it!