Son being abused , can i go to the cops?

My son is 17 years old. He’s had this girlfriend since January and they hadnt seen each other in a while due to covid. However these past few weeks theyve been allowed to see each other since restrictions were lifted .

Last week I noticed him and his girlfriend fighting more on the phone. I asked him about it and he shrugged it off. Well today they went for a hike and when he came back he was hurt. His eye was swollen and his lip bleeding a bit. His phone was also cracked. I asked him what happened and he said nothing. Then i asked again and he said he fell. However I didnt notice any scratches or anything else on his body. Just his face. Something didnt feel right to me so I kept a close eye on him. Well since his phone was cracked and not working I had let him use an old iPhone of mine just to use apps like Instagram and stuff. While he was taking a nap I opened the old phone and admittedly went to his Instagram to look at messages. His girlfriend kept blowing up his DMs . So i clicked on it. Immediately i see messages of her accusing him of being with another girl because he wasn’t replying. She was cussing him out, calling him names, etc. i scrolled up and just an hour before she was apologizing to him for hitting him and breaking his phone. She’s the one that gave him a busted lip and swollen eye. From what I gather they had an argument because he was liking girl’s pictures on Instagram. And he ended up apologizing to her even though she was the on that hurt him! At this point I was LIVID. It took everything in me not to reply to her.

I then woke him up and asked him what really happened. Let him know i saw the messages and that he needed to stop seeing her. I also told him we needed to file a police report because what she was doing was wrong. He started yelling at me that it wasnt my business and I needed to stay out of it. I tried talking to him calmly and explain that he was being a victim of domestic violence but he wasnt having it. So I told him he wouldnt be able to use the old phone anymore because I couldn’t trust him not to speak to her and that he wasnt allowed out with her anymore

I want to do more. I want to go to the police. But im not sure if I can even do that since Im not the victim. Does anyone know if i can? His girlfriend is his age. I just dont know what to do. I dont want to punish him for being a victim but I definitely dont want him seeing her again. However i know teenagers tend to go against their parents and I dont want to push him away from me right now. I need some help ladies.