You should do something to properly prepare you muscles for any type of exercise. Ideally, you would warm up for 10-15min then stretch your muscles. You are probably fairly young, so it won't matter as much for you now as it will later. Just make sure that you do a proper warm up before progressing to the more physically demanding movements.
Stretching after a workout can help prevent soreness a little bit as well, so if you stretch for a little bit after each training session, you would benefit from it. Also, stretching regularly will build flexibility more than anything else. It's always useful for a freestyler to be more flexible.