It will probably work, but I would not recommend it. Ryzen CPUs depend on RAM performance and running a single stick of RAM in a dual channel motherboard is going to hurt performance.
If you go with one stick now and get another later, that may not work as mixing and matching RAM does not always work well togther, even of the same model. This is why RAM is sold in kits as they are tested to work together.
In the end, it should work, but it will hurt performance and may cause a headache down the road. I would also spring for 3000mzh or higher RAM. Look for a 2x4gb kit of 3000mzh DDR4 RAM>