There are two ways people approach this situation when it comes to Phals...
some people will keep the spike once the flower drops, hoping for a second bloom. Others cut the spike down after the bloom drops and waits for it's next bloom cycle.
I prefer to cut down the spike. In my opinion, even if the spike blooms a second time, those blooms are usually not as spectacular as the first one was. I'd rather cut the spike and allow the plant to put all it's energy into itself and producing a fabulous bloom on the next cycle.
Some Phal species are known to produce keikis (babies) on their spikes so those shouldn't be cut unless they are brown and shriveled. The standard store-bought Phal is most likely not in that group.
Your Phal will be fine, just care for it until the next spike comes along
I also don't put cinnamon on cut spikes. I only use it if there is an open wound on the plant itself. Adding cinnamon wouldn't hurt the plant but it really isn't needed on spent spikes