It means he had no other choice in his opinion. I agree with your point and if this was a real life matter, it would be very unlikely that he would be left off the hook. He would have been killed for sure. I'll write what I wrote above again: He could have told the truth and been put into the Witness Protection Program very easily but Larry was dedicated to the mob so he chose to instead say it was someone else who whacked Overall. He straight up lied to the government. I suggest you actually watch The Sopranos though, that way you can see the relationship between Tony and Larry.