Keeping a long story short - me together with Coworker B made a meme about Coworker A and circulated it in our room, which is what I thought was a group a close friends both in and outside of work (5 people) who know each other well.
When I came back to the room after break, I jokingly said we should print it out and put it on Coworker A's desk (A was present in the room). He ran up to me and pushed my hot chocolate in my face, spilling it all over me and the desk.
I've never been in this kind of situation, what should I do?
EDIT: We had a talk and ironed out everything. I apologized for making the meme and he apologized for overreacting.
Not going to explain all the details and I still believe this was a massive overreaction no matter what all the comments are saying - the chocolate wasn't extremely hot so I'm not injured, but he had no way of knowing that at that moment.
One comment mentioned that I'm lucky that was the least of A's reaction, but if getting your face burned is an acceptable (and I should be counting my blessings for being a jerk) punishment for an image (no matter how malicious) then I don't even know what to reply to that kind of person.
In any case, thanks for all your replies and helpful comments! :)