What Causes Itching And Extreme Tenderness In The Vagina?

Hi...im a 25yr married woman..I have an iud so I don't have a period very often but I did a few days ago..I had sex w my husband on the last day of it..It only lasted two days n we went to the river and I woke the following day w some tenderness but that was it..only to wake the next morning w swelling n itching n exterme tenderness..i have taken tyenol n used ice packs but I still have some swelling around the vaginal opening..not sure if its a rash or something more