The CPS will have to decide between two possibilities.
1, what you said at first was true and he did hit you and cause the bruise
2, what you say now is true and he did not hit you.
As you have been told it is VERY common ( in fact almost normal) for the victim in domestic violence cases to retract their initial statement.
Just look back through AB law questions, the 'my partner hit me but i have withdrawn my statement' question comes up about once a week!
In the majority of cases the reason the victim ( usually a woman) withdraws their statement is because they are too scared of the attacker to continue with the case. I am NOT saying this is what happened here but it really is what happens most of the time.
The CPS will look at the case and they, not you will decide to continue or not.
My guess is that this trial will go ahead, the fact that your BF has 'previous' and that he is on remand suggest to me that the police think this is a serious case. You say he was already on a community service order when this happened what was that for?
Sorry, but a man already doing a community service order is arrested for an assult of his partner that is considered sufficiently serious for him to be held on remand. How does that look to an out sider.