I missed your statement you have had recurrent oral herpes for years. That makes it almost impossible that HSV-1 is the cause of the genital problem. If you have herpes, you can expect it to be HSV-2. Please report back with both your own and your partner's HSV-2 blood test results.
Also, consider asking your doctor again about a culture (or PCR) from the genital lesion. Being "unconvinced it was herpes" is the most important reason that you SHOULD be tested.
Welcome to the STD forum.
The most common cause of genital ulcers -- and it sounds like that's what you have -- is herpes. A single lesion like you have is most consistent with a recurrent outbreak, although it certainly could be an initial one. As for HSV-1 versus HSV-2, I don't understand how your doctor concludes HSV-1. Either HSV-1 or 2 is possible, but the latter is a more common cause of genital herpes, especially if you have been infected for some period of time, i.e. not a new infection.
You are correct that auto-infection (self infection from another infected area on the body) is rare. Assuming this turns out to be herpes, it either is either 1) a previously asymptomatic infection you have had for a long time, only now causing the first obvious outbreak (this is quite common, accounting for almost half of all cases of apparently new genital herpes infections); or 2) a new infection from your boyfriend. If it is the first of these, almost certainly the cause is HSV-1. If the second, it could be either HSV-1 or HSV-2.
The implication of the second explanation, of course, is that your boyfriend is infected with one of these viruses. If HSV-1, his infection probably is oral; if HSV-2, probably genital. Since 20% of the adult population has HSV-2 without knowing it, it is a possibility your partner is infected despite absence of symptoms.
So the answer to your first direct question is yes. In fact, the large majority of new genital herpes infections are caught from people who do not know they are carrying the virus and have no symptoms. Might it be something else, perhaps related to your cold? Yes, that is possible as well. This may not be herpes at all.
What to do now? Several things, preferably right away:
1) If not yet done by your doctor, your genital sore(s) should be tested for HSV, preferably by a PCR test or possibly with a culture test. The sooner the better; these tests are most accurate when done within a few days of onset. If this shows HSV-1 or HSV-2, it will nail the diagnosis for sure.
2) Have a blood test now, for both HSV-1 and HSV-2.
3) Your boyfriend needs to be examined and should also have HSV-1 and HSV-2 blood tests.
Taken together, these results should determine whether or not it is herpes and, if so, whether you are having an initial or recurrent infection, the virus type, and whether your partner is the source. In the chance the answers aren't clear, and if your blood tests is negative for both virus types, a final fall-back would be for you to have a repeat blood test in 2-3 months to see if the results has turned positive for HSV-1 or 2.
In the meantime, you should be treated for presumed herpes, with one of the standard drugs (acyclovir, valacyclovir, etc). The drugs are far more effective when started early, rather than waiting for confirmation of the diagnosis, which could take several days.
Finally, don't be freaked out about all this. Even if your boyfriend is infected, probably there is no "blame" in it. He most likely is truly unaware and has no symptoms. In addition, if it turns out you both are infected, then the worst has already happened: you cannot re-transmit it to each other, i.e. there are no "ping pong" back and forth infections.
Please report back when test results are available or when the diagnosis becomes clear.
I hope this helps. Best wishes-- HHH, MD
I should also add that I am getting a blood test for HSV2 on Monday, so that could provide some answers. However, my doctor did not perform a culture test on my sore because she was unconvinced that it was herpes, and said that the test is often inaccurate. She also could not give me any other explanation for the sore of the top of her head.