As a recently graduated Internaltional Student in Australia, the Temporary Graduate (485) Visa is your path to continuing to live, study and work in Australia.
One of the legal requirements for working visas in Australia (including the 485 Visa program) is that you provide proof that you have the right health insurance.
This means moving from your current Overseas Student Health Cover (OSHC) policy to an approved Overseas Visitor Health Cover (OVHC) policy instead.