Someone crash into me (21m)

In the morning, when I was going for work, as soon as I took a left trun towards the company gate, some Old man(50+) hit me from behind. And he fell on the road and blames me saying it's my fault for taking a turn, and I should have showed him a hand, when I turned, he say I was Speeding and he was slowly on his way. Also he was trying to drag me out to beat me up and my company mutts (watchman) didn't even see anything but it's his fault. That old man was saying pretty toxic words and was cursing me, No buddy is taking my side, what to do help me pls, should I call the police. He said I wait for you to come outside, he is a senior citizen, am I allowed to fight back in self-defense?