/u/restricteddata is your go-to person on anything atomic-related, but in the meantime, here is some information on the bombs from our FAQ (please note this is not to discourage further responses):

http://www.reddit.com/r/AskHistorians/wiki/wwii#wiki_the_atomic_bombs

The short answer to your question is that the bomb was not close at all to being used on the Western Front in WWII, because it wasn't finished until after the war in Europe ended.

The longer answer to that -- the timing of when the bombs were finished and what went into building them -- is a good question for someone like /u/restricteddata.

The related question -- of whether the Allies would have used atomic weapons on Germany -- may well veer into the realm of speculation.