Hello Bachido members,
it’s been about 2 weeks since I started practicing shamisen and I’ve encountered my first problem. I know as you strike the ito, the bachi is at a slight angle. I’ve been trying to become more aware of what angle I approach as I strike since my knuckle occasionally hits the kawa first. I was wondering if there was a correct way to create this angle, whether it be made with the wrist, the arm, or the way the bachi sits in the hand.
The primary advice I have is that you shouldn’t expect yourself to be able to hold the shamisen and the bachi optimally for at least a half year.
That said, I encourage you to whenever something feels awkward, think it through and try different techniques.
Generally speaking the striking should come from the shoulder, moving the whole arm, while the wrist isn’t involved as much except for a slight rotation between each strike.
Which knuckle is touching the kawa? Your index finger? Then you need to angle it more.
Welcome to Bachido, C Sak!
That is top notch advice that Karl has on expectations. When learning shamisen or any instrument, keeping expectations low is very important. Stay in the mindset of ‘playing’ (experimenting) with the shamisen, not caring what’s “right” or "wrong. The first priority is taking time to just get comfortable.
If it starts to get frustrating, take a break for a few hours or a day. Allowing the mind to back away from the problem means that when you come back to it, your mind comes in from a new angle/perspective, allowing the solution to potentially reveal itself clearly.
If you’d like, feel free to post a video of your playing. We can take a look at how your striking and might have a few ideas for you to try. 
Thanks for the replies. It was middle finger or pinky knuckle that kept hitting the kawa. Taking all of your advice, on closer inspection, it seems my forearm wasn’t hanging far enough over the dou and was situated in the middle, making my hand uncomfortably close to the kawa.