What were the effects of Lenny crushing Curley's hand, and why was it an important event for each of the characters?

Curley picks the fight and Lennie finishes it. The little man trying to prove himself tougher and smarter than the man who is perceived as weak as he is slow minded. The direct result of Lennie's reaction is to anger the boss' son, put their jobs in jeopardy, and set himself up for retribution.