I am 18 and a half weeks pregnant with number 3 and I've discovered a small pimple sized lump on my outer labia. It's very dark, like some sort of blood blister (dark purple-ish) it's quite raised and perfectly round..feels  to the touch like a skin tag and isn't painful. Is it cause for concern, and will it go away on its own if I just leave it? Thanks in advance for any advice! X