The scar is irrelevant
The trauma that produced the scar is of interest
Like everything, it is how you provide your history
If you say you cut your face, were fully examined by a qualified doctor who told you you had suffered no other injury, and were sewn up, you have no problem
If you say you had other injuries or tests or can't remember or didn't understand all the X rays and blood tests and the night in ITU don't be surprised if they start digging. And rightly or wrongly doctors are often afraid to say there were no other issues. They say things like 'a head injury couldn't be excluded'
So within the realm of telling the truth.....