Here's the most egregious case of circumcision gone wrong, but there are plenty of others. It's not a no-risk operation. As for the child not remembering the pain - prove it. Just because something can't be remembered consciously doesn't mean it's not locked in our body memories.
$1:
David Reimer (August 22, 1965 – May 5, 2004) was a Canadian man who was born as a healthy male, but was sexually reassigned and raised as female after his penis was accidentally destroyed during circumcision.[1] Psychologist John Money oversaw the case and reported the reassignment as successful, and as evidence that gender identity is primarily learned. Academic sexologist Milton Diamond later reported that Reimer failed to identify as female since the age of 9 to 11,[2] and that he began living as male at age 15. Reimer later went public with his story to discourage similar medical practices. Eventually he committed suicide, due to suffering years of severe depression, financial instability and a troubled marriage.