Hi, i have a large red bump on my labia that is painful. it popped up out of nowhere. i don't have any stds, what could this be?

Several possibles: Labial bumps as you describe could be ingrown pubic hairs that become infected, sebaceous glands that become clogged and infected, pimples that become infected, and abscesses. These are the most common causes and are relatively benign if treated. Simple pimples and ingrown hairs usually resolve on their own, but infection require antibiotics and occasionally drainage.