I started running in college and built up to running 6 miles 3-4 days a week. I made the terrible mistake of not taking stretching seriously.
The result: 2 seriously annoying injuries. I developed runners knee and ITB syndrome. Initially I took some time off and strengthened my quads and hamstrings which allowed my runners knee to heal. However, I have had ongoing issues with ITB syndrome.
Make sure you warm up properly, you need to loosen your tight hips before you run, and make sure you stretch afterward.
Here is a fabulous post-run stretching routine I found to make sure you cover everything.
Stretch. Do it. You’ll be glad you did.