The victim should be consulted but it is the State's ultimate determination. I suggest you apologize to your cousin through some other family member. Perhaps take care of his medical bills if any as a start.
PTI is a prosecutor's program. The victim, he is not a plaintiff, has input since he is the prosecutor's witness. The prosecutor can let you in over this objection or can they can reject. The position of the victim is one of the factors to be considered, 2C:43-12 (e)(4), for rejection but the prosecutor can easily fit the rejection within one of the other guidelines as well.