How do i tell him i have a boyfriend?

So Imma Freshmen.
and theres this guy I just met.
I kinda figured he liked me
bc I would be wlking down the hallway and he would smile at me.
that went on fr 2 weeks.
I was wlking and saw him.
I was about to pass him
and well I guess the floor was wet...

so...
I trip.
he stopped helped me up, carried my books and walked me to class.
we became friends.
his name is Sparky
Hes a Junior
and hes really popular.
BUT--- I have a boyfriend.
and don't know how to tell Sparky.
I sorta like him too.
hes really sweet.
well my friend lives next to him
and Sparky told her he likes me.
He doesnt know I know.
I don't want to hurt Sparky.
But I don't want to hurt my boyfriend.
help??
thanks if yu do:]

Just explain to him that you already have a boyfriend, but you are perfectly cool with just being friends because you think he's a really nice, sweet guy.