Speaking to Chelsea's official channels after the match, Charles said: "We created chances but we should have created more as well. The chances we did create, I think we can look and say we should be putting some of them away.
"Sometimes that's just football. We know ourselves that we can be so much better. [We had] all the shots but not many on target, that's immediately something we have to look at. We'll have other chances in the group. We want to win every game but it's not the end of the world, but we know we can be a lot better."