What can I do to make battery charges go away?

Me and my boyfriend got into an argument and he got physical. Left me with a concussion. But I do not wish to press charges. The way the police got involved was because she posted on Facebook about the event and someone reported it. My boyfriend lied in his police report and is willing to come forward and tell the truth. We just want this to go away. And deal with this privately. We are 18. What can we do? Do I have to testify against him if I marry him? What are our options?