About 18 days ago, I visited a massage parlor.  The masseuse gave me a normal massage.
At the end, she masturbated me with her hand, and French kissed me for about 5 seconds plus or minus a couple seconds.

I'm not worried about the hand-job.  But, about 12 days later, I had developed a feeling of slight pain in the back of my throat and thought I was getting a cold.  Fast forward 5 days later, it still stung a little to swallow but not terribly bad.  The pain was always pretty mild, not extremely  painful like an aphthous ulcer.

I read you can catch syphilis if someone has an open syphilis chancre in the mouth.  It can be transmitted like that via kissing.
It looks like any ordinary aphthous ulcer, but it doesn't hurt as bad.  It is mild compared to that, but looks similar.  What are the chances this could be a syphilis chancre for primary syphilis, given that she is a massage parlor lady at a shady establishment.  Should I get tested?  It was such a short kiss and not very deep.  I have a history of over-thinking these things and worrying too much about STDs.  Maybe this is like that, but perhaps not.

Thanks.

1. .  Syphilis is a relatively rare disease and most syphilis currently occurs among men who have sex with other men.  Most persons, even most CSWs working in "shady" situation do not have syphilis.  

2.  Most syphilis occurs at genital or rectal sites.  Oral syphilis is very, very rare and when is occurs lesions are typically visible (on the lips or anterior tongue).

3.  Syphilis is transmitted by DIRECT contact and transmission is facilitated by friction. It does not sound like there was direct contact with your uvula, nor meaningful friction.

4.  When persons are exposed to partners with ano-genital syphilis, transmission occurs less than 1/3 of the time.  Transmission rates are likely substantially lower for oral syphilis.  

5. Syphilis lesions are typically not painful.

Bottom line, the likelihood that this is syphilis is very, very low.  if you remain concerned (I would not be), then have a syphilis blood test- once the lesion has been present 2-3 days blood tests would certainly be positive.  

I hope this perspective is helpful.  I would not be worried.  eWH