Check with CA counsel. In some states, a scenario like this could trigger a claim of "strict liability" (which would be advantageous for you compared to negligence).
I believe CA is a strict liability state regarding dog bites. The attack should have been reported to the police and animal control.
If you failed to do so then, do so now. Document all your costs from the incident and either bring the dog's owner to court yourself or retain counsel to do so. The CA and your county bar associations can assist you with referrals.
The foregoing is for general information purposes and does not establish an attorney-client relationship.