1st anwser is, run or no run you should stretch for about 15 min every day. And if your about to do something active or anything, stretch ALOT. (when i go to run, all i see is people get there Quads and Hamstrings.. Thats great but you need to stretch you knees and calves alot also)
Second.. What do your legs hurt from.. Is it a pain that you know you've been working out too long.. (your legs are burning
Or is it that you know you haven't stretched your maximum and legs are hurting from that ??
If its from your legs are hurting because you've been working out them and your trying to push yourself, then IMO it doesn't really matter. Your getting a workout and the more you push yourself the better the results.
Note: Your legs will be pretty sore...
But if its from a bad stretching routine then definetly stretch more or change it. You can seriously injure yourself if you dont have a good stretching routine or dont stretch at all before putting your legs through such work. Its just not the right thing to do.
Edit: Like the person above me said, when you run dont run on pavement or try not to. Its bad for your knees.