J.R.
Has he said why he doesn't want to practice? Is it a situation where you are critiquing him while he's practicing, so he doesn't feel like he can make mistakes? Or is it that he's too busy doing fun things and he just doesn't want to stop?
If he really likes the lessons, can you tell him that he won't be able to go if he doesn't practice? And maybe make the lessons a really special time for him, like go out for ice cream with him afterward.
Also, if it's truly only 10 minutes a day, maybe try to find a concrete way of showing him just how short a time it actually is. Maybe make a specific time of day practice time, just so that he gets into a routine with it.
I hated practicing piano when I was his age. My parents made me practice 30 minutes every day. I finally convinced them to let me have Friday be a no practice day. But I did it for 11 years, and I never got as much out of it as I should have because I hated it so much and it was more a battle of wills with my parents.
I am planning to start my almost 5-y.o. in piano lessons and am hoping that we don't have a similar battle of wills over practicing with him.