Help! please! im in ALOT of pain!?

i was inserting a tampon when i was on my period and the plastic bit at the top was sticking out but i shoved it up anyway quite roughly. Afterwards i noticed i was in a lot of pain and had to take the tampon out and it hurt so much i cried with the pain. There was alot of blood on the tampon andit couldnt have been from my period bcause it was only in for about a minute. Thats when i realised that i must have cut myself with the tampon. Its now three days later, my periods over but im in ALOT of pain! it stings so much when i pee and it hurts when i sit down. i have to change my knickers about 5 times a day because they are all blood from the cut inside my vagina. i dont know what to do its soo painful :( can someone please help me!