You need to delete apps from your "My Library" on bn.com, they can't be deleted directly from the NC.
Only B&N apps can be installed on the NC, unless you root your NC. (There are hundreds of posts about that on the NC boards...) They keep adding new apps, slowly. When they add more and what they will be is always a guess, though there are many who hope they are something other than the enhanced books for children!
I went to BN but could find no way to delete apps from My Library. I could see it for books but not the apps. I would like to get rid of the Nook Friends app and possibly one or two others.