On Thursday evening, Friday, and Saturday of last week, I could feel a minor pain in my right quad. At first I ignored it, because I thought it was probably from my sitting at my computer for several hours on Thursday. The pain was very weak, and I didn't notice it much during the day. However, I had a slight difficulty walking, because my right foot felt weak, and, my knees felt a bit weak when going up stairs.
After my run Saturday morning, I decided I'd better do something about the pain, to prevent it from evolving into an injury. I stretched my quads during the rest of Saturday, several times on Sunday, and this morning before I ran. As soon as I stretched my quads, I could feel a reduction in the pain, and by Saturday afternoon the pain was gone. It was also gone on Sunday and so far today.
The moral of this story is that if you experience an abnormal condition in your body, don't ignore it because it may get worse; give it appropriate treatment. I usually don't have any pain in my body, so that minor pain was abnormal. If I had ignored it, it might have evolved into an injury.
Even though I haven't had the pain since Saturday morning, I'm going to continue stretching my quads for a few days.