You can click the lock icon in the top bar of FB and it brings up many of the privacy settings. I double check mine twice a year.
I just go down the line in each section and do it one by one - most have drop downs with options.

If you have the name of that person you can block him by adding his name in the "How do I stop someone from bothering me" section.
The little arrow drop down next to the lock icon has a help section that explains things.