The issue is whether, under all the circumstances, they were careless or negligent--that means *unreasonably* careless, and not that they did not take every precaution which  they theoretically could, since no one is held to the standard of absolute care, just of taking reasonable care. If they were careless, then that could be malpractice; but even if so, it's probably not worth bringing the case. Malpractice cases are expensive; you need to hire a medical expert, and they do not come cheap. Meanwhile, what you could recover as compensation is commensurate with the injury done you and any additional costs. If you just had to put up with a few stitches for a few weeks, and then maybe the cost to remove them, you could not recover enough money to justify the time and cost of a lawsuit.