I'm not a Dr, physio etc but I would give it a go if I was in your situation and see what happens. I would start with short slow runs on soft ground and keep an eye on the knee. If the pain does not return I would be delighted and if it gets bad again at least I would have tried it and got an answer.
But that's just my personal opinion and not the one of a medical professional.
Well done on stopping smoking and losing weight! Just get out there tomorrow and enjoy yourself. I also doubt you will be last with your time but the most important thing is to have fun. So go and do it. You have done all this training so please don't doubt yourself. You will feel great crossing that finish line. Good luck and let us know how you got on.