An example of external conflict in "the lottery" is:

the chivalry's most valued code is morality

for this, you need to remember something significant in your own life, for example, if you were bullied when you were younger, you can mention your memories on this and touch on how such treatment can harm other kids your age either physically or mentally. (racism, car crashes, a parent in the hospital are all very good subjects, think hard on it! )

hope i ! : )