I want to say that all this in good natured discussion.

We don't know many of the facts -- was your injury quite severe or will it heal within the week? Did/does this person have a propensity for violence and
intended to cause you serious injury or did a rare occasion happen that drove this person to lose some control, act irresponsibly and do something that he would and should be sorry for? You reported him once before and we don't know the severity and whether it was two months ago or 6 years ago. We also don't know where and how the injury occurred.
What would you expect or want to happen? What kind of jail time -- 24 hours? It sounds like you think he deserves a lot more. I know you are mad and you have a right to be. Two weeks? That could easily ruin a person's livelihood as that person would have to inform work that he/she could not report, etc. Should that happen here? I'm trying to balance reality and practicality here. NY considerts types of assault as Class A misdemeanors meaning a sentence that can be greater than 15 days but no more than 1 year.
A DA deals with rape, robbery, brutal assaults, drug distribution, murder, manslaughter and the list goes on. Unfortunately it costs a good deal of money to incarcerate and generally there is a shortage of space in our prisons. Practically, I really don't know how far a DA would prosecute a person for throwing a phone if it wasn't meant to cause you serious injury and didn't cause serious injury. At the very least, there are civil remedies available to you so that you can punish him in the wallet and that should teach him a lesson. If it did cause you a serious injury then maybe this will go further.
On a side note, under the law "assault" is strictly a verbal threat to cause injury, e.g. "I'm going to strike you now in the head with this baseball bat." Battery is the physical act and they frequently occur together ("assault and battery").