It depends on how much stock you made, how cool it got in those 20 minutes, and what else is in your fridge.
Basically the reason you cool it before putting it in the fridge is so the heat from the stock does not raise the temp inside the fridge thus bringing everything into the danger zone (40-140 degrees F). If your stock is going to raise the temp of the fridge to that range then it needs to be cooled more before you stick it in there.
Now if you only have things like ketchup, lettuce, soda, and things that would be OK in the danger zone then it really doesn't matter much.