Depends. Rightfully/legally in most places it was your deer because you had the final kill shot.
Given this fact "nicest buck I ever shot.", Personally I probably would have kept it (but not sure...given it was a kid and his first deer it would have been hard not to give it to him)...but depends on how many opportunities you get to hunt and your chances of dropping another animal before the season ends. Depends on if you rely on the meat to feed your family. So basically a lot of factors to take into account.
Hopefully you have some good luck coming your way because I think it was very generous of you to give the deer to the young hunter and maybe just knowing you did a nice thing is more reward than keeping the deer.