I agree that he may be attempting to communicate, and that he may be frustrated and/ or angry because he is unable to effectively communicate his needs. My mother says, before I talked enough for her to understand what was going on, I used to bite her and scream a lot. She said it used to happen when my daily routines were broken (this could be changes away from favorite foods, toys, tv shows, etc), when I didn't like or want something she was repeatedly trying to get me to do, or if I couldn't have or do something I really wanted. It would also happen and she couldn't figure out what the cause was. Back then, she didn't know that I have ASD. I have a lot of sensory issues, and I think that the times when I acted out and she couldn't understand why, it may have been because I was overwhelmed by things in my environment (certain sounds/ loud noise, textures of food or things touching my skin, too many people around, etc). I was unable to express that feeling of being overwhelmed any other way, and could not make the things in my environment, that were overstimulating me, stop. So, I think I did whatever I could to try to make it stop.
For people with sensory issues, certain stimuli (light, noise, touch, texture) can cause severe pain or nausea, muscle tension that causes pain, or other unpleasant physical reactions that others may not be aware of. Routines are important for people with ASD because it helps us to cope with stimulus in the environment, by giving us a familiar reference point/ safety zone. This is important when your environment has a lot of things in it that are scary or very unpleasant (ie. overstimulus), especially to a child. I think that whenever your nephew is acting out, it might be helpful to try to find a way of communicating with him. Calmly, tell him that you can't understand what he is trying to tell you, and that you want to help him. Ask him to show you what is wrong or what he needs. If he cannot sign or use a tablet, it might be helpful to enroll him in a program for young children with ASD. Perhaps they could help teach him ways of communicating. It also might be helpful to try to reduce some of the stimulus in his environment. Maybe something is setting him off and he is so overwhelmed, all he can do is react. I recently learned from my therapist that it can be psychologically very traumatic for a child with ASD to constantly be exposed to overstimulus, when they cannot make it stop, and for them to frequently be in situations where they feel unsafe. This can lead to childhood PTSD, which can in some cases, result in violence toward others or self-destructive behavior.
