I have a small lump on my vulva! Help?

You'll definitely need to see your doctor. Just tell your dad you're having "female issues" and you need to go to the doctor. I'm sure he realizes you're growing up and will experience these things. No need to tell him exactly. He'll probably not want to know if you say "female issues" anyway. Most men shut up and shut down when a woman says that. (LMAO)