Hello 123cali,
Once an injunction is served, it is effective immediately. After service, not adhering to, or breaching the injunction, could be considered an arrestable offence. The specifics of the rules of the injunction should be detailed in the paperwork, which you should have a copy of, to double check.
You can also contact DV Assist who are a specialist injunction service, who can answer any questions: https://www.dvassist.org.uk
Take care,
Lisa