What Causes Bumps On Labia That Bleed Heavily Upon Popping?

I have a small tiny bumps/spot on my labia which are not painful at all, however when I pop them HUGE amounts of blood seems to come out to the point of having to wear a panty liner/sanitary towel. Before, during or after popping the bump does not hurt or itch or irritate in any way except the excessive amount of bleeding. Please explain what this spot is and why its caused?