The Crown Prosecution Service takes the view that there are TWO 'victims' in an assault case. One is, obviously, the person who is assaulted but the other is 'the law of the land'. Even if the person who has been assaulted doesn't want the case to proceed, 'the law of the land' has still been broken and a prosecution would normally still follow.
That's particular so in domestic violence cases, where the CPS is aware that victims often come under pressure from the offender (or from others, such as the offender's family or friends) to withdraw their statement or to refuse to give evidence in court.
The actual policy document that prosecutors work to is long and complex (you can read it here
http://www.cps.gov.uk/legal/d_to_g/domestic_abuse_guidelines_for_prosecutors ) but it basically boils down to saying that a prosecution should ALWAYS go ahead in domestic violence cases unless there are extremely exceptional circumstances. That would apply even when, say, the offender had simply pulled the victim's hair; it's even more likely to be followed through when the level of injuries sustained by the victim reaches the 'GBH' level.
However, in this case, it's possible that the offender's legal team might seek to get the charge reduced to 'ABH'. That's because a 'GBH' charge can only be sustained if there are 'really serious' injuries. The CPS's own guidance states this:
"Grievous bodily harm means really serious bodily harm. It is for the jury to decide whether the harm is really serious. However, examples of what would usually amount to really serious harm include
injury resulting in permanent disability, loss of sensory function or visible disfigurement;
broken or displaced limbs or bones, including fractured skull, compound fractures, broken cheek bone, jaw, ribs, etc;
injuries which cause substantial loss of blood, usually necessitating a transfusion or result in lengthy treatment or incapacity;
serious psychiatric injury. As with assault occasioning actual bodily harm, appropriate expert evidence is essential to prove the injury"
http://www.cps.gov.uk/legal/l_to_o/offences_against_the_person/#a15
The offender's legal team might seek to show that your injuries didn't fall within those categories. (Note: you'll see that my web link refers to 'Section 20', rather than to 'Section 18'. That's not an error; the same criteria apply to both charges).
It makes a very big difference to the offender as to whether he's found guilty of 'GBH with intent' or 'ABH'. With an ABH conviction (at the more serious end of the scale), he might get away with perhaps 6 months imprisonment. For GBH with intent the sentence might be closer to 6 years:
https://www.sentencingcouncil.org.uk/wp-content/uploads/Assault_definitive_guideline_-_Crown_Court.pdf