starting again

First of all, let me welcome you to BT.  I am happy that your foot is better and I wish you all the best in your tri quest.  What type of tri were you training for last year, sprint, oly, half?  You not be thinking of your run training distances in terms of distance but rather in terms of which pace and intensity your foot will be able to sustain without injuring yourself.   As for the time of training for your run, that should be commensurate with whichever training plan you have opted to follow.  In other words, if your training plan calls for 30 minutes of running at race pace, run for 30 minutes but at a sensable pace, one that will not cause you any discomfort or pain.