Yes, it's accurate, and you should get the sore checked out. Any time you get a sore on your genitals, it warrants a trip to the doctors.
The timeline for a syphilis sore, called a chancre, doesn't fit from the encounter you had a year ago, but if you've had any other encounters since, you may need a test. It could be something other than syphilis that needs treatment - herpes, a fungal infection, an infected hair follicle - it's a long and varied list of possibilities, but you should get it checked.