Hey demurex,
Welcome to the boards!
Unfortunately, we are not able to make diagnosis over the internet. So the short answer is that making an appointment with your healthcare provider is a great next step.
To ease your herpes worries:
1. Given your sexual history, that it is just one bump, and that it has not come with other symptoms, it seems very unlikely to me that this would be a result of herpes.
2. But also to do a little myth-busting: Herpes is, by no means, the end of the world! Millions of people on earth have it. There are two different strains: HSV-I and HSV-II. In North America, almost 50 percent of adults have HSV-I and around 16 percent of adults have HSV-II. If you want to learn more, check this out:
The STI Files: Herpes.
That being said, you should get it checked out by a healthcare provider--in person, they will be able to give you way more info. Maybe it's an ingrown hair? Maybe it's a pimple? Maybe it's something else? You will know soon! Given that this has been concerning you a lot I'm sure that peace of mind will be a relief.
A few questions for you:
Have you had a gynecologist appointment before? The American College of Obstetricians and Gynecologists recommends that people with vulvas/vaginas first see a gynecologist when they're between the ages of 13 and 15, so if you haven't gone yet, as a 17-year old now would be a great time to start! And that alone can be the reason you tell your dad for going, you don't need to get into the specifics of the bump if you're not comfortable! [And to be clear, the doctor will not tell him because of doctor-patient confidentiality laws.] How does this sound? And know who to call/feel comfortable setting up an appointment?