If the pistol had been loaded (assuming, of course, that it was an accurate shooting one and properly sighted), you would have had a central bull's-eye for your shot. Most likely, however, you will find that the pistol came up all of a tremble, and that, as the hammer fell, the front sight was jerked very wide of the "bull" and perhaps even hidden by the hind sight.
Do not be discouraged, but cock and try again. By the way, it is best to use a "dummy" cartridge or an exploded one whilst doing this "snapping" practice, as otherwise the jar may do damage to the plunger and perhaps break the mainspring. There are dummy cartridges, made with a rubber "buffer," for this practice.
If you still find your hand shaky (and it is not naturally so), it most probably arises from your gripping too hard.
The action of "letting off" should be like squeezing an orange--a squeeze of the _whole hand_. Start with a light grip when your hand is down, and gradually squeeze as you come up, the trigger-finger squeezing _back_; and the hammer will fall without the least tremor or without the sights moving off the point they covered during the fall of the hammer. The main thing of all in pistol shooting is to _squeeze straight back_. Whenever you find yourself shooting badly see if you are not "_pulling off to one side_"; and in nine cases out of ten you will discover that this was the cause of your bad shooting.
Some men can never squeeze the trigger straight back, and have to allow for this by getting the hind sight "set over" to one side to correct it; but this is a slovenly way of shooting, and, as the pull to one side may vary according to the "jumpiness" of the shooter, it prevents his being a really first-class shot.
Keep the hind sight perfectly horizontal; beginners are prone to cant it on one side, which puts the bullet to the side towards which you cant.
After a little practice, you will be able to "call" your shots, that is to say, you will be able, the moment the cartridge explodes, to say where the shot has struck the target, as you know where the sights were pointed at the "squeeze-off."
After six shots, make a pencil-cross over each bullet-hole, so as to know where your former shots hit. After twelve hits it is best to take a fresh target. At the end of the day's shooting, you can cover the holes by pasting black patches on the bull's-eye holes and white on the rest, and use the target again.