Ever tried kicking with shin guards┐
Pain is normal in the beginning. Without shin guards kick at a level of force where you just can take the pain so you can continue to throw the next kick. Have a good warm up before kicking. While kicking, try not to think too much about the pain as that will focus your attention on it and thereby you feel it more. Put some loud music on and maybe think of someone you really dislike so you mind gets distracted and your adrenaline level gets raised which serves as a natural pain killer. Over the next weeks you can then gradually raise the intensity of kicking.