The laws in Australia have come a long way recently, however it's still impossible to get a prescription from a doctor to try these types of things out, even though it's now legal to, and it sounds like they'd be perfect to treat the pain I live with and have been taking opioid based medication for the last 12 years to cope with. Unfortunately even if you could find a doctor authorised to prescribe it, the cops could cancel your drivers licence for having it "in your system " with their new and improved roadside testing. So improved that you could return a positive test day's or weeks after consuming anything containing thc or the like... so you could get busted, even with a doctors prescription, AND even if you're in not at all under the influence... unlike the roadside alcohol breath test which measures the level of alcohol in your blood, there's no legal safe level, so ANY amount is automatic disqualification of your drivers license...
Makes me so mad! Wake up Australia!

Anyway, I hope you continue and find some relief from your accident and injury. Man, as I get older I realise how fragile our human bodies are, and something trivial like falling off a surfboard can cause a life changing injury... good luck with it!