QANTAS, is like pretty much every other airline. No visible tattos while in uniform.
You will need to use a flesh coloured plaster. Depending on the size of your tattoo, it may not be that noticable. Your watch will probably partially cover the plaster.
There are some special makeups that covers tattoos. I have not tried it, but might be worth a go.
Camouflage makeup concealer for blemishes tattoo