Jay
For what it's worth, I think you should be guided by your body but be prepared to become the boss if you need to. I know that sounds contradictory, so I'll try to explain.
With a new (last few days) injury - if it hurts at rest, stay resting, as HE says.
If it's OK at rest but hurts when you are moving it, that's your body saying that you are doing more damage or preventing the healing. Keep resting for a day or two.
After that, a minor injury (over-extended ligaments/muscles etc) get set in their ways and they will start to hurt when you try to get them back to a full range of motion. That's when you need to boss them around. Walk and run-walk to get them going but be aware of the level of discomfort - it should be discomfort only, not pain.
Whatever, build up gradually. Don't expect or try to do your normal distance for a few sessions.
In the mean time, try a low-impact exercise, bike, swim etc to keep the cardio-vascular fitness building.
I do waffle on, don't I? Better shut up now!
Saxplayer