Julian Carter wrote:Is this a substantial part of the film,and do I really need to worry that I'm missing on those 2 seconds? Thanks.

I dunno. Did you miss it? Did you notice something was missing? If not then I would say don't worry.
The BBFC (because of the British law) will not allow violence that may be copied by a child easily on "U" movies ("U" stands for "Universal" and there are no age restrictions). Depending on the context of the violence, it may be asked to be removed from "PG", "12" and even in some cases "15" certificate movies.
This is a new ruling though. Until recently, easily copied violence wasn't allowed on anything below a "15" and even then some "15" movies were edited (The Matrix was edited to remove headbutts).
The change in the policy explains why two of the new Ultimate Bond DVDs are released "uncut" for the first time ever, and how the DareDevil movie was edited for the cinema, but released uncut by the time it got to DVD.
In theory I agree with the "U" ruling. After all, it would be easy for a young child of 4 or 5 to copy something that they have seen on a DVD, and head butt a child in the playground, and potentially cause a major injury. However, it seems a bit pointless when our TV has no such restrictions (and if I remember correctly, shows like Grange Hill and Byker Grove used to include head butts).