Male bettas build nests when they've got breeding on the mind, which basically means that they think the conditions are right for spawning- clean water, plenty of food, and being in good health. So yes, it means they're happy. But like Amunet said, some males just never bother with nests so don't take a lack of nest as a bad sign.
I am guessing your betta has not been in contact with any females... Right? Because if you have one of those supposed "Community setting"s There is a high risk they have spawned. Other than that He is probably happy, and is ready to breed