Okay put down the pitchforks, people ... Nick tells TMZ, he and his GF of nearly three years -- a chick named Breana Tiesi -- have been tossing the idea of marriage around for a while now ... so the engagement isn't supposed to be a big surprise.
What is the big surprise is the engagement ring -- which Nick says he purchased VERY recently to pop the big question in the next few weeks.
He wouldn't give any details about it -- but if we were to guess ... it's probably round with some kind of rock on it. Congratulations!!!!