4 weeks ago i was with a someone who wanted to perform oral on me. I allowed her to perform it for a few seconds than stopped her. Now i see a skin discoloration and its not a bump on the shaft, just raised skin (on the shaft). There is not any pus or white stuff in it, but i'm a bit worried. Is it possible to acquire syphilis from a 15 second blow job? How do you know if you have a chancre? Or could it just be from a scratch of a tooth?