What Causes Red Rash Around Vagina After Sleeping With Tampon On?

I just tried a tampon for the first time a three days ago. I m 15 and am a virgen. I put in the tampon before practice after school and accidentally fell asleep with it still on when I got home. I woke up the next day with small red rash like bumps around my vagina. I have not had any pain or discomfort. The tampon was a light flow one. I ve read about TSS and am really hoping that I don t have that. I have not experienced any other symptoms. What could this be and will it cure on its own or do I need treatment?