[Q] Noob Alert.. Question Nandroid backup.

First of all I woild like to thank everyone out there in the community, you people are just amazing.

Okay see the backup we make through recovery of the rom..i think it is called nandroid backup. but just correct me if i am wrong.
okay the main point is that.. we dont generally do a dirty flash when flashing a new rom..
i have made a backup from recovery and i want to do a clean install of a new rom.
how can i restore my apps?(any other method instead of making apk backups and reinstalling)
I want to restore my data of certain apps also? ( like the additional data file of real racing 3 )

thank you
anyways the backup i made is on ext sd card.
:)