Hello I Recently Had Protected Sex, And A Few Days

Hello
I recently had protected sex, and a few days after discovered a lump in my labia minora, it had a slightly brown appearance was slightly tender and felt like a lump. It was circular but a lot smaller than a marble.

I also today developed some stinging sensation when urinating, but I have just started my period so I'm not sure if this is related to that or if it is a STD