I have over 80+ fights. So I hope my advice can help.
For starters, NEVER strike someone with an object (such as a lighter) wrapped inside your fist. Your fingers will break instantly! Whoever told you that watches too many movies. Not being disrespectful; just informing you.
In martial arts, it is often said, "Hard target, soft weapon. Soft Target, hard weapon." What this means is, if you are striking to the head (namely the face), you can use your palm to strike. And, if your striking to the body (such as the stomach), you use a knee or an elbow or even your fist. The head is considered a "hard target". The inside of your hand (your palm) is considered a "soft weapon."
However, you CAN use your fist to strike a "hard target" such as someones head. You can. You just have to be careful when doing so. If you break your hand in a street fight, you're in tremendous trouble. To learn how to strike a hard target with your fist involves learning how to strike both ACCURATELY and EFFICIENTLY. If you are a "headhunter" - a person who likes to aim for the head - then accuracy is important. Don't just swing for the fences and aim for the entire head. This can lead to a broken hand. The forehead is the hardest part of a person's skull. You accidental hit there, the chances are high of breaking your hand. So don't swing like a crazy man. Be accurate. be precise. Aim for three targets ONLY: The jaw, the nose, and the temple.
Your ACCURACY involves a little practice. If you have a punching bag, get a role of tape and place an "X" at both the location of the nose and the chin. Pick a height that is equivalent to your height. Begin striking these targets, first moving slowly, feeling your arm extend outwards and how your body moves when you do this. Strike from a defensive position - both hands up moderately high. Keep doing this over and over and over and over and over again. After time, you'll notice that your capable of striking the target with better accuracy AND, that your strikes should feel a little more solid. And use both hands; don't just favor one.
If you keep practicing, in time, your body will become more EFFICIENT at performing this range of motion. AND, your hand will become used to the shock and better capable at handling it. I'd advise certain wrist exercises to also prevent your wrist from buckling, such as squeezing a tennis ball, or curling a 1-2 lb. weight isolating just your wrist.
Once your body has become accustomed to striking these targets, you can then work on your POWER. Power can come not only from your arm, but also from stepping into the direction of your target, or a slight twist of the hips. Again, work on this over and over and over and over and over again, starting from just throwing a punch (preferably a straight jab) to combining the punch with the little movement (ie. stepping in to or twisting the hips) to increase the power behind the punch. In time, with practice, your body will confirm to this range of motion and you will become more comfortable with this motion.
YOUR HURT FINGERS: I'm guessing your were swinging wildly in a circular ("roundhouse") motion and made contact with your fingers rather than your knuckles. (I'm not certain why your fingers would be hurting.) Either way, here is something else the world of martial arts has taught me: IT'S NOT HOW HARD YOU HIT, BUT IF YOU HIT HARD ENOUGH. To knock out a person only requires so much power behind the strike. You do not have to put everything you got into one swing. Hell no. This, again, only increase the chances of you breaking you hand. Keep hitting that punching bag over and over and over again until your strikes feel solid and you can move the bag around. And imagine what it may feel like from being hit in the face by your own fist. If you feel that it would really hurt, your getting there.
The practice on the bag will mold your hand to a more solid weapon. Wrist exercises will prevent your wrist from buckling during a strike. Keep your fingernails cut short. When making a fist, simply curl your fingers inward and keep the thumb out. But honestly, a palm to Anyone's nose (rather than a fist) is just as effective. Really.
I have small hands, thin fingers, and thin wrists. Wish I had big sledgehammers for hands, but i don't. But i have accustomed my hands for speed and accuracy and have enough hitting power to knock someone out. Am I the hardest hitter on the planet? No. But I do hit hard enough and have knocked plenty of opponents out. (Plus, I use my elbows quite a bit.) I'm not boasting. I'm just telling YOU what YOU are capable of.
Hope this helps.
11-2 record in Iron Stripe circuit as "Freestyle Stiker", 2+ years American Kenpo (AKKI), 9 years 8 months prison (seven of those years inside a Texas Gladiator Farm).