http://bettatalk.com/how_bettas_spawn.htm
The bubble nest is just that...a bubble nest. He's feeling randy and he's looking for a female to get it on with.
The bubble nest is there to show the females that he'll be good about caring for the young-uns, and for actually holding and protecting the eggs and the very young fry.
The article above will show you the way that they spawn.
Your Betta is fine.