What Causes Pimple Like Bump In The Vaginal Area?

I seem to have maybe caught an infection. I have only been sexually active with my partner however he shows no syptoms similar to those that I have. I had recently attended a camp and during the stay I started my period. Nobody at the the camp had any pads or tampons for me to use so I had to resort to using toilet paper. a day or two later I noticed a bump on my vagina. it started of as an itch then greq into a sore filled with pus and blood thereafter. it has since healed. A few days later I felt a pain on the inside on my right vagina lip, during this time I was still using the toilet paper. when I opened to see what it was it seemed to be bumpy pimples next to one another. it then flattened out with a white colour in the middle. I have not been experiencing any unusual discharge or odour. could this be a reaction from the toilet paper or could this be an Sti?