You shouldn't use tampons until you've had your six-week postnatal check. This is because you'll still have a wound where the placenta joined with the wall of your womb (uterus), and you may also have tears or cuts in or around your vagina.
Using internal sanitary products like tampons and menstrual cups before this wound has healed could increase your chance of getting an infection.
After giving birth, you'll have vaginal bleeding, also known as lochia. It's similar to a menstrual period, but can last between two and six weeks.
It'll be very heavy at first, and will get lighter over the weeks. You're advised to use maternity pads or sanitary towels during this time while your body is still healing.
Read more about bleeding after childbirth.