Tell your BF, you like to give the phone in son's place. That is

Tell your BF, wither is your BF phone or your new phone, you just like to give your son. That is your love to show to your SON.

You can return the phone and nice tell your BF that your son got a phone...

If in the date time, he is not conside your feelings, how can he be good later...

Usually, after you talk, I believe he will be OK (If he still like you a lot...)