It probably sounds strange, especially at such a young age, but he may just be getting embarrassed that he hurt himself. I have experienced this with my son since he was younger (he's 4 1/2 now), and I have tried to explain to him that we all get hurt sometimes. We fall, we trip, or someone bumps into us, and sometimes it's just an accident and that it's okay. He seems to get really embarrassed if he trips or falls in front of other people which just results in him getting angry and shouting or trying to hit. Sometimes it's better to just step back and see what happens as long as he's okay, and let him come to you for comfort. Our instinct is to run and help them and make a big deal out of it such as oh no, are you okay, which usually scares them and just makes them more upset.
I have always tried to act like it's not a big deal and say something like, uh oh, you fell, but you're okay. Sometimes that works and sometimes not, but you'll know if it's more than just a little bump or stumble.
Good luck.