Stress fractures normally don't show up on an X-ray until about 3-4 weeks after the break. Even at that point one usually doesn't see an actual crack, but often can see some thickening of the bone where the fracture is healing. In their early stages they're often diagnosed by severe, localized pain directly over a bone, especially in areas like the feet where the bones are close to the surface. At any rate, they don't heal in times as short as several days. If the area looked bruised as well as swollen, you might have just broken a small blood vessel in your foot. That would heal relatively quickly as the blood was resorbed.

If you can now walk without pain, you should be OK doing a short test run. If all goes well, proceed and ramp back up.

I would not get fixated on the possibility of a stress fracture. Had one or not, it did or didn't happed and will heal eventually, if you give it time. Don't take lack of immediate pain as proof of healing. You could be in for further injury if you do, regardless of actual cause or effect. It is more likely you pulled or dislocated a joint, ligament, tendon, muscle, etc. (ie:sprain/strain). Regardless of whether there is a stress fracture or not, there is definitely something wrong with your footwear, running surface, or foot. Granted, hot running tends to get sloppy, but your dogs are supposed to hold up to all that pounding, barring any accidents. When they don't, there is more to look at regarding the inherent stability of your anatomy and gear.