I can be pissy-vindictive but usually after my feelings are hurt. I tend to withdraw and then even poke a bit to make sure the other person realizes I withdrew. If they hurt me badly I just cut them off entirely, so I would suggest he does still like you if he is still engaging. It is our Te misbehaving.
Typically it is short lived as I forget stuff quickly and then realize my response was defensive and emotional. reactive is a good description. It is also a sign of learning to cope with hurt-ie being a bit young. Over the years I have realized the pattern and then tend to withdraw quietly for a few days to sort out the emotional response logically before engaging, or self correct before letting irritation take over.
I would suggest not calling it immature or pointing out it is overreactive. Instead take the Ni grounding approach and be a solid point of stability, let him get pissy, then forgive him as you understand he is kinda like that. INTJs are funny as I will emo dump at them and they just go "really?, silly enfp come sit down and chill out"
When interacting with enfps be certain not to mistake this short lived pissy Te response with a Te logical argument that has Fi passion. This is where my worst fights with my ENTP friend have arisen.