Blackheads and pimples are not rare on the penis; there is no explanation why one appears at any particular time, any more than a similar lesion of the forehead, shoulder, or anywhere else. You could try pressing it out, but gently; if you express a core, just as you would on your face, it would a) confirm that diagnosis, b) "cure" the lesion, and c) preclude the need for a doctor visit.
It could take 5 pages of writing to explai the symptoms of herpes, warts, and other STDs. Do a little searching on your own. You will find the descriptions do not match what you describe.
Thank you for the response doctor. If I may, how does a male get a pimple or blackhead on the shaft/head of the penis? How long will it last and will it go away on it's own? Should I try to squeeze it or leave it alone? Should I be concerned?
Also, what are the symptoms of herpes, warts or other common STDs on the penis?
Again, thank you.
With apology, on this forum we do not examine posted photos -- in fact, MedHelp administration deleted the link to the one you posted. However, from your description, this sounds like you probably just have a blackhead or pimple, not an STD. Or given how small it is and difficult to see, maybe it is nothing abnormal at all. Herpes, warts, and other STDs seem unlikely. Whatever you have, it isn't something you caught during the recent sexual activity with your girlfriend. My guess is that you're just looking too closely and it may have been present all along.
If it persists, follow through with your plan to be professionally examined. I'm not sure you need to see a dermatologist; your primary care provider might be equally capable of diagnosing it. But in the meantime, I wouldn't worry; this doesn't sound like anything important or serious.
Regards-- HHH, MD