Hi, Thank you for posting your question here, I will try to answer it to the best of my abilities. Yes it can be an STD, but it can also be due to him being huge and well rough sex. It could have cause some minor damage in your vagina, which is swelling now and that could be causing the itching. You re feeling it one day because at that time you were full of adrenaline so you dont anything. It is only later one that the pain shows up. So wait a couple of days, it should heal on it own. If it is still itching after that, go to a doctor and tell them about it and they can check if maybe you have a yeast infection or vaginosis. I hope this answered your question.