Should i apologize to him?

So I was at a school assembly sitting in the floor with my class and I'm naturally tall. So this kid behind me is complaining I can't see except I'm bending down for him. I also have mild scoliosis so I kinda need to have my back straight so I don't get lower back pain in my future. So when the kid moves a bit his friend gets really angry and starts kicking my back when I'm curled In a ball since there are a lot of people around me. Later I'm grouped with the kid that kicked me in PE and he won't respond or try to practice for the PE test. Should I apologize to the kids or ignore it.