Cos I'm in a lame mood, I went and got all my training stuff out which I have to run through every time I'm stuck doing first shift inductions:
"No jewellery is to be worn in Fresh Food departments other than a plain wedding band (no stones), one small closed sleeper in each ear, and/or an approved medic alert necklace/bracelet if applicable.
[In other departments], no more than two studs/sleepers are allowed in each ear. No other visible body piercing is permitted; this includes tongue piercing. [Yadayada about necklaces and keeping to a minimum]"
So, yeah. As townie says, speak to your department manager on your first (?) shift, if you're not in a Fresh Food department, and they may be willing to compromise, whether this means a small piece of skin-coloured tape or leaving it fully exposed - it'll likely depend on the manager of the department and the store. If you are in a FF department, the State Health Department Food Safety Acts prevent you from wearing nose jewellery, regardless of religious observances.
Hope this helps
PS: The case referred to above by townie is described as follows: "THE AUSTRALIAN INDUSTRIAL Relations Commission has held that a Woolworths employee should be allowed to continue wearing a nose stud at work, but not while handling fresh food or when in contact with customers...She also noted that another employee, who worked as a checkout operator, was allowed to wear a nose stud because of her religious and cultural beliefs." Source:
http://findarticles.com/p/articles/mi_qa5393/is_200604/ai_n21390548/pg_1?tag=artBody;col1