Vaginal lump

Hello, I have a small lump/bump almost like a pimple in my labia minora. It only hurts when I pee and it feels like when you put lime on a cut. Do any of you have an idea of what causes them and how to alleviate the pain? Or treatments? I am sexually active and I’ve done tests so I know it’s not an std. Any advice is helpful so please help me out. Thank you!