Would not worry to much mate, as secondary poisoning if it was only a rat it would not have enought poison in its system to kill your dog, might end up being sick if that? would clean out the cut and keep your eye on it, was at the vet with my lab last year and it ate something along those grounds and vet gave me the all clear and it was more than a rat and that had been poisoned!
Thanks for that mate, ive cleaned her up well and given her antibiotic, usually they drop the rat as soon as theyve shook it, but thats because there ready for the next one, this lil b*****d entered the wro