Get tested and stop worrying. Syphilis is curable so whats the big deal. Worrying doesn't fix the problem.
Be vigilant about your testing, 6 weeks and beyond is recommended.
The infectiousness of syphilis depends on stage and treatment status. You were at risk only if she had a recently acquired infection that had not yet been treated. If your partner's syphilis had been diagnosed and treated with penicillin one day or more before your exposure, or if she has late or latent syphilis (over a year since she was infected), you were at no risk even if you hadn't used a condom. With condom protection, then probably you aren't at risk regardless of stage and treatment.
The skin problem on your thigh doesn't sound like syphilis. However, every person who has been exposed to someone with infectious (potentially transmissible) syphilis should be treated with penicillin, regardless of condom use.
Bottom line: see a doctor about it. Ideally, maybe see the same doctor or clinic where your partner was diagnosed or is being treated. If that isn't practical, at least get all the available details from your partner about her diagnosis, treatment, etc.
Good luck.