i whipped my hair back and forth and now my neck hurts a lot?!

You tightened up your neck muscles when you did that and now you have to free them back up and here's how to do that:
Neck
Put your hands alongside your head so your thumbs are on the front of the muscle under your ear and your fingers are on the back of the muscle behind your neck. Squeeze your thumb and fingers together and hold. Relax your body. When your fingers and thumb touch, about two minutes, slowly lower your head as far as you can, release the pressure but hold your neck lowered for another 30 seconds.
For best results relax your body first by taking a deep breath and exhaling then remain this relaxed.

Stop whipping your hair back and forth. If you have no choice them cut it short. As for the pain it will go away in a few days. Try rotating your neck very slowing a few times. Paracetomol will help the pain and if you lie down flat on your back you will heal quicker. Unfortunatley there' no quick fix but don't worry , it'll get better in a few days :)

you sprained your neck.

1. Warm Compression
2. If it hurts so much you cant move - Ibubrofen
3. Soft Neck brace.

Don't do it again
My friend did this and knocked herself out, I guess she didn't realise quite how close the wall was...

GOOD !
looool :D

lool

Thats what you get for taking orders from a NINE YEAR OLD!

*facepalm*