The Kettlebell Swing is a basic Kettlebell training exercise which trains the hamstrings, lower back, and hips.
It is the prerequisite for all other Kettlebell movements, and hence is one of the safest Kettlebell movements out there.
However, just like any other movement out there, there is a risk that you will injure yourself if you do not follow some simple rules.
Here are 8 ways you can injure yourself while swinging a Kettlebell:

1. Not warming up properly.
   A cold muscle has a higher chance of getting injured than a warm muscle.
   
2. Using a weight that is too heavy.
   
3. Not letting momentum do its work.
   Success with the Kettlebell swing is all about the hip snap.
   It's a power movement.
   Not one that relies on raw strength.
   
4. Not getting the technique down properly.
   If you're having trouble with the technique, then keep practicing.
   Use Youtube, purchase a Kettlebell guide, or ask a friend to teach you.
   
5. Letting the Kettlebell control you.
   Kettlebell training is all about controlling the Kettlebell.
   If you do not tighten up and control the Kettlebell, you're body will be flapping all over the place and you'll end up pulling something.
   
6. Bending over too much.
   Keep your back straight, abs tight, and chest out with every single movement (unless otherwise stated).
   
7. Doing stupid challenges.
   There are some dumb challenges going around, such as the 10,000 swings in 30 days challenge.
   This is stupid because such a training program does not allow your body to recover probably.
   
8. Not recovering properly.
   With that said, don't do swings every single day.
   Rest and switch it up with other movements.
   Eat and sleep enough.