Whats the difference chancre and canker sores?

Infection vs. immune. A chancre is an ulceration that is one of the stages of having the std syphilis. A canker sore or apthous ulcer is caused by an immune reaction or trauma. The chancre needs treatment via antibiotics to be cured and the canker sore is self limiting and heals on its own but does recur.
Different diseases. Chancre is a painless ulceration most commonly formed during the primary stage of syphilis. A canker sore is usually caused by the herpes cold virus.
Don't want chancres! These are three type of sores that cause confussion, 1: canker sores, which are in the mouth 2: cold sores caused by oral herpes usually on the or around the lips, 3: chancre sores caused by syphilis usually on the genitals.