Get your solicitor to seek information regarding the exact nature of the victim's injuries. If you broke the guy's nose, 'ABH' might be the correct charge:
http://www.cps.gov.uk/legal/l_to_o/offences_ag ainst_the_person/#P189_14382
However, if you only bloodied his nose, 'common assault' might be more appropriate:
http://www.cps.gov.uk/legal/l_to_o/offences_ag ainst_the_person/#P92_3540
(It makes sense to ensure that you're charged with the correct offence, since 'ABH' carries a much higher potential penalty than 'common assault').
'ABH' is an 'either way' offence, which means that it can be dealt with by a magistrates' court or referred up to the Crown Court. (A Crown Court can impose a prison sentence of up to 5 years, plus a fine of up to �5000). In practice your offence will almost certainly be dealt with (in a matter of minutes) solely by a magistrates' court. You'll probably be given a community sentence (of, perhaps, 100 hours unpaid work) plus a fine (of, perhaps, �300), plus costs (perhaps �80) and a 'victim compensation scheme payment' of �15.
Chris