I don't know of any STD's, herpes included, that look like small black dots near the tip of the penis. My best guess is that this is a small scab from friction from sex. I recommend that you not pick at the spot, just apply vaseline or th equivalent to it daily. In the unlikely event that it doesn't go away in 10 days, show a doctor.
If you are very active with more than one partner, of it your girlfriend has a potential STD history, you may want to be checked for STD's in general. But again, the black dot sounds traumatic, not infectious.
Take care.
Dr. Rockoff