B.H.
He may be playing with sounds and doing it deliberately. If he doesn't do it constantly and it get's better I wouldn't worry.
My daughter stuttered from 2-6 and ocassionally still does. I've had her evaluated by speech several times and she doesn't do it at school only around me when I'm rushing her or she's nervous. Its just a nervous thing for her.
I was told to Slooooooooow down, get to eye level with my daughter and give her eye contact. That works really well for us.
See if he does it around other's when your gone.
Typcially from what I've heard it's hard to get kids into speech even for a evaluation til they start school. And at 2 years old when they are still learning unless it's super serious they won't touch them.