Hi, Ok So I'm A Little Worried... After Sexual Intercorse

Hi, ok so I'm a little worried... after sexual intercorse i get one or two sores on the perineal area, only there - nowhere else, a little like moist craters or grazes but only this time i have larger cut type sores, only way i can describe is it looks like a large paper cut on both sides from top to bottom... they have the same pain as the other sores, both extremely painful and combined with severe itching. I dont know what is going on, my sexual parter is relatively new, hes not on "the small side" so wondering if thats anything to do with it but we are planning a life and i dont want this hurting me everytime we are close... i hope you can help me.