There doesn't even need to be contact for an assault let alone an injury.
It is the "apprehension" of unlawful personal violence with is the assault as such. That is a mere belief, that the victi, will be assaulted.
Similar to robbery (in very laymans term, a theft with violence), a belief that the suspect had a gun, knife will wallop you one, is enough.
If he is any friend at all he should testify in your defence (slightly different in co-defendant cases) but your solicitor should sort it out.