You should consult a physician. Usually a prophylactic regime of the anti-rabies vaccine is considered for the possum bite. Meanwhile you should wash the place of the bite under running water with soap, continuously for 10 minutes. Read the resource, under the heading, "Do opossums carry rabies?";
Please feel free for your follow up questions.
What are the chances of infection at the bite site, I would have thought very small. I couldn't find anything on the net about what to do if you get bitten by a possum so I am assuming this is a very unusual case.
Yes this is quite common. Very rare to get any infection if you wash it thoroughly. Apply the Dettol or better would be povidone iodine (betadine, won't need prescription). Keep the bite site open (don't dress it). Still it is better to talk to your GP.
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