New 3DS XL Home button not working.

Yes, you need to buy a new home button and install it. If you have a bit of experience taking things apart it shouldn't be much of a problem. If you're not that confident you can also take it to a repair shop/send it to Nintendo. If it costs more than 20$, try to get it cheaper somewhere else because the replacement part is about 3$ and it would take me about 5min to fix it...