Hello. What you are experiencing is normal. The inner walls of your vagina and cervix were not used to being stretched to such an extent by a well endowed penis. Which is why they took a little more strain than usual, resulting in a sore vagina. The aftermath of such a scenario is the body s response to try to get your vagina (made of smooth muscles that help in stretching of the vaginal walls, and later contracting back to the pre-stretched state) to return back to the state it was in before its inner walls were stretched. During this period you shall be sore, but when you introduced a tampon the walls of the vagina which were still healing were stretched once again, making you feel exactly how you did after the session of intercourse. Do not worry about it. Try using a sanitary pad instead of a tampon this one period. You should be able to get back to tampons from your next menstrual cycle. Hope this helps. Best wishes.