If after a week the insert fell out, will I have to buy a new one, or will the doctor put on another one?

As I understand it, it is about an intrauterine device. If so, please read on. It seems to me that your question is whether the doctor will want to consider that the loss of the IUD is a consequence of some error during the application and will use a kind of "complaint procedure". Unfortunately, this is very difficult to resolve. Contractions of the uterine muscles during menstrual bleeding can sometimes cause the system to move or fall out spontaneously. This is more likely if a woman is overweight at the time of setting up the system or if she has had heavy menstrual bleeding in the past. Therefore, the extension of the insert does not have to be associated with a defective insertion. While the application of an intrauterine device can be reimbursed as part of the services from the National Health Fund, its cost is always on the patient's side. In private offices, the benefit often includes both the cost of the insole and its establishment. I have a feeling that the doctor may offer to put on a new IUD free of charge, but he will not want to bear its cost - this is just my guess and you should talk about it directly with the doctor. I enclose additional information: https://www.gdziepolek.pl/produkty/43342/levosert-przyrzad/apteki/w-warszawie