I understand what you mean by a tooth-like device. You were expecting the hammer to look like the hammer on a cap and ball pistol or a single action cartridge pistol. No, it is supposed to be flat as you have found out. I am glad that you changed the nipple because you often run into rifles and pistols that have been dry fired many times and it has damaged the nipple to the point that the gun won't fire a cap. Never, never :nono: dry fire a caplock rifle because it will damage the nipple if there isn't a cap on it to absorb the shock of the hammer striking it. There is no problem with dry firing a flintlock, though. That's okay and no damage will be done.
Okay, you have changed the nipple and it seems to be working better. Now, the thing to do is to thoroughly clean the lock. No telling what it was last oiled with nor how or how long it has sat. Some oils will gum up if they sit for a long time. Here's what I know to be the best way to clean a lock. Go to your nearest auto parts store and buy a spray can of either carburetor cleaner or brake cleaner. Both will do the job so buy whichever is the cheapest. Remove your lock from the stock by placing it on half cock and then removing the lock bolt located on the side opposite the lock. Usually there is only one bolt holding the lock in place but occasionally there are two. Use a screwdriver to carefully remove the bolts without messing up the slot in the head. Once you have it (them) out, the lock will lift out. Sometimes you may have to wiggle it a little bit to get it out. Once you have it out, take it and your can of cleaner out into the driveway away from cars or other painted surfaces that could be damaged by the solvent in the cleaner and thoroughly flush out the lock. Be sure to use some eye protection because that stuff really stings if you get any in your eyes and it sure can't be good for them. Be generous in your spraying because you want to flush out all of the crud that is in there. Then, if you have an air compressor, use some compressed air to blow your lock dry. If you don't have a compressor, just shake off the excess cleaner and let it air dry. The solvent is pretty thin and will evaporate quickly. Once it is dry, lightly oil the workings with something like Remoil, 3 in 1 oil, etc. Wipe off any excess oil. The inside only requires a light oiling. Excessive oil will only attract more crud. Replace your lock into the stock and replace the lock bolt(s). When you tighten it (them) down, they should be only snugged down. Over tightening the lock bolts will cause lock problems by crushing the wood fibers in the lock mortise and making the lock rub in places where it should not. Just gently snug, not King Kong tight. At this point, your rifle should be firing caps on the first try. :thumbsup:
Oh, by the way, while you have your lock out, it is a good idea to take a toothbrush and brush out the lock mortise to remove anything in there that might be lurking and waiting to get into your lock works and causing more problems. Just give it a good brushing.