Separation anxiety of 2 year old.

Hello my boy is 27months old and he has a separation anxiety from his grandparents. As he has grown up till 21momths and far away from his dad and when we came to his dad at21months he is fine every month grandparents used to come and visit him. But in 24th month we went to because his father was affected with covid we stayed there for one month. When we went there his behaviour has changed very much always crying and always want to be with his grandpa that too in car only. Not in house. Then we came to his dad's place 25th month. Now he is showing sadness frustration and angry on us both. He is hitting and biting his dad whenever he remembers them. And he is getting cry but he himself is turning his cry to laugh and he himself is trying distract himself am really worried about his behaviour. To consult a child psychologist online cost is more I can't afford it. Please help me out what I need to do to make my son feel better we both play with him for hours he is habituated to videos