Took away his gifts

I gave a tv and a laptop to my girlfriends son on his birthday. I am not the father. We do not live together. Me and his mother can get in some really big fights. Last time we fought I took the tv and laptop and left, to hurt his mother and not him. But I did end up hurting him and now theyre both so mad at me... I havent seen them in a week. I tried going back to give back the tv and laptop but she doesnt want me to give it back. I am still speaking to her on the phone everyday and she miss me but she thinks I went too far this time. What can I do to fix the situation !? My main concern is the kid I feel so bad for what I did... I want to fix it but I don't know how. I feel like going and giving it back again is just not enough and now he will thinks I'll just take back his gifts anytime I want. I REALLY never wanna do that again...

The kid is 9.