A cicatrix is the scar that's left behind on skin after a wound has healed. That raised mark on your hand where you burned yourself on a hot pan a few years ago? That's a cicatrix.
You're much more likely to use the word scar, but cicatrix or cicatrice is common medical terminology, so the nurse who bandages your skinned knee is definitely familiar with this term. In Latin, cicatrix means "scar," and it's been used in medicine since the 17th century. Botanists use it too, for scars on tree bark: "You can see the cicatrix where they pruned that big branch, near the top."