I would probably advise against it but it all comes down to personal circumstances. In terms of was there massive obstacles to you doing well, you didn't put enough effort in or just didnt do well academically. If it's the first case then maybe repeating is something to consider, but for the other two I probably wouldn't because there is no way you can guarantee you do the HSC again and you might just fall back into the same habits, if that was the case
Aside from that honestly the ATAR and such might seem like the most important thing in the world in your position and you might think that it will dictate your future degree and success capabilities etc. This isn't completely the case, unless you wanted to do something like medicine or law which then it's basically near impossible to get in without good marks (which even if you do the HSC over again doesn't mean you are going to get that mark the second time around so there is a risk of wasting a year). In most cases you could just spend a year in uni doing a different degree and do well there and then transfer into what degree you wanted to do, and the extra bonus is maybe some of your units will transfer across or can count as electives so you don't actually get too back tracked in your overall degree path
You also need to understand although maybe a majority of your assessment is finished now, you still have trials maybe and the HSC exam to go that is still more than 50% of your mark that can change, if you were able to improve on your marks. But at the end of the day it's your decision to make and I wouldn't personally just make it off what other people online tell you. You should consult with your parents and teachers at school, on what is your best path forward as they will probably know your situation more in depth and be able to recommend the best advice for you