Hi! I would like to connect my LED lights (Vaxmyra from IKEA) designed for 24V system into my 12V system, do I need a current limiting resistor?
The PCB is likely designed in the same way that LED strips are meaning that the series LEDs are expecting a 24V rail like shown below,

If you deliver 12V to a strip expecting 24V the voltage divided between the series LEDs doesn't add up! You would need to in theory half the length of the series LED paths for 12V to work and that's not going to happen. No single component is going to fix this problem, without a new PCB design or a 24V supply.
Your only option would be to step up the 12V supply you have to 24V but that seems like more of a headache than it's worth.