The bump may not be a genital wart. The doctor who can tell you best is a dermatologist.
Even if it is a wart, it doesn't mean you caught it. People get warts all the time--on fingers, legs, and genitals, without having contacted anyone who has a wart. So I understand your perplexity, but you don't have to worry about that.
I would suggest that you be checked to see if it is a wart. If your wife goes for regular Pap smears, as she should anyway, then she will be checked too.
Whatever the bump is, the doctor can burn it off in a flash.
Take care.
Dr. Rockoff