You don't say where you are or details about your new partner, but I'll start by pointing out that syphilis is exceedingly rare in women's in most geographic areas and most types of sexuality of the US and other industrialized countries. On that basis alone, syphilis isn't likely. And 9 days after exposure is atypically early for appearance of a syphilitic chancre (10-20 days is more typical). Also your description of the anal area lesion doesn't sound much like syphilis, and I have to be more suspicious of an injury from the sex toy. However, herpes also is a consideration -- in fact, herpes due to HSV1 from oral sex probably is the most likely STI in this situation. However, even this seem relatively unlikely, since newly acquired HSV usually causes more than a single lesion and most cases would be noticeable sooner than 9 days after exposure. Still, it's something to be considered. That you were able to express "white pus" fits best with folliculitis or other superficial non-STI infection. Pain versus painless really says nothing much about the likely causes -- even though syphilis chancres tend to be painless.

What other sexual exposures have you had in the last couple of months? Do you have sex only with women or also with men? Have you ever had oral herpes (cold sores)? Genital herpes?

You need to be examined in person, ideally by a doctor or clinic highly experienced in STIs. It isn't possible to be more certain about the possible causes based on the information available so far. Please don't be tempted to simply go to a lab for self-chosen testing. As implied above, testing probably should include an HSV test from the lesion and perhaps an HSV blood test. A syphilis blood test is needed, not because it could be positive this soon but as a baseline in event later testing is advised. Are you in a place where expert care is likely to be available, e.g. near a public health department sexual health clinic?

Finally, you should discuss this with your partner. For example, does she have oral herpes? If so, might she have had a recent outbreak?

I might have more to say if you can fill in the information I've asked about. In the meantime I hope this information is helpful.

HHH, MD