You can block anyone from contacting you. You can also block them from sending nudges, or instant messages. 
On the email, just look below their text, (near the right side of the page) you will see the "block user" link. 
You can also block from Instant messenger. 
Nudges can be blocked. To the right side of the nudge, you will see "block user" 
Blocking from any one of these features will block all three. 
In addition, when you click "report user" on the persons profile, you are given an option to block. 
* You cannot block someone from viewing your profile. Profiles are public. 

For more detailed instructions, you may also want to see our help section, located at the very top of the page. 
http://mingle2.com/welcome/help