As long as it's not serious, it doesn't reach the point of sewing, and you can run after the pain stops, and it doesn't affect it. If the collision is serious, you need stitches, and you need to wait for the wound to heal completely and recover for a while before running. However, running is harmful, so it is suggested to change running to brisk walking, which will do much less damage to the knees and achieve the purpose of losing weight and fitness. Walking for more than 40 minutes consumes more calories than running.