What Causes Painful Blisters On Labia Majora?

A day ago I noticed two pimple like bumps/sores outside my labia major and then today there were two more on my labia minor (they are swollen and hurt), there are also some bumps further into my vagina which appear to have black tissue around them... (I am not sexually active. I have sports practice everyday for a couple hours.) I don't know what's going and I'm getting scared. Please offer some advice, thank you