Hi Lab
Sorry for the delay in responding to you. Unfortuntaley, you are going to have to wait for the police to complete their investigation to determine whether you are liable for any offences whether it assault or any public order offences.
In answer to your question regarding sentencing for assault, please see attached link for general guidance. (no visible injury or discomfort only injury is consistant with Common Assault, page 23).
http://sentencingcoun...ine_-_Crown_Court.pdf