Despite the harrowing moment Elba said the whole experience weas "great".
The on-screen tough guy also revealed his softer side, adding: "I can't stand seeing children suffer. I watch Toy Story and I start crying so let alone Beasts Of No Nation!"
The Hackney-born actor, who found fame in US series The Wire and has starred in Marvel's Thor films and won a Golden Globe award for his portrayal of late South African leader Nelson Mandela in Mandela: Long Walk To Freedom, became a father for the second time to 19-month-old son, Winston.
"He's a good boy with me, really bad boy with his mum because she spoils him, I don't," he said.
"I am the tough guy ... I am actually a doting father. I pick him up a bit but for some reason he just takes the [mickey] with his mum."
Elba admitted balancing his hectic work schedule with fatherhood can be tough.
"It is tough. Most times if I can, I'll bring my family with and we'll just sort of live but that's really tough because I do long hours and I never see them and I'm always grumpy so there's no point. It is tough, you've just got to spread it out a bit," he said.
- PAA