As the owner, you are responsible for your dog. Report the incident to your liability insurance for any damages incurred and to the veterinary office. Self-reporting is usually the better way.
From a legal point of view, a dog bite can constitute damage to property in the sense of Art. 144 StGB (Strafgesetzbuch), assault in the sense of Art. 126 StGB, injury in the sense of Art. 122 ff. StGB or even a killing in the sense of art. 111 ff. StGB represent. Since a dog cannot be a perpetrator under criminal law, its owner or handler is responsible for the act.
According to Art. 56 Abs. 1 OR (Obligationenrecht), the owner of an animal is liable for the damage caused by the animal if he does not prove that he exercised all due care in the care and supervision required by the circumstances or that the damage would have occurred even if he had exercised such care. According to Art. 56, Abs. 2 OR, the right of recourse is reserved to him if the animal has been irritated by another or by the animal of another. In principle, the animal owner is always liable for the damage caused by his animal, but under certain circumstances he does not have to pay for the damage or only partially if he can prove that he did everything in his power to avert the damage and the damage nevertheless occurred - for unforeseeable reasons.
Generally, disputes are covered by liability insurance policies. These factors play a role:
Power of disposal:
A liable animal owner is one who has the so-called "power of disposal" over an animal. The power of disposition over an animal is, for example, who provides for its keeping and maintenance and can determine the use of the animal. The concrete circumstances are decisive.
The concept of damage
For Art. 56 Abs. 1 OR to apply, there must be damage. This is primarily understood to mean financial damage that can be quantified in francs and centimes.
The causal link
The causal connection is the relationship between the cause of the damage and the event that occurred. The question here is whether the event for which someone is responsible is to be regarded as the legally relevant cause of damage. A liability of the animal owner presupposes both a natural and an adequate causal connection. According to this, every event is naturally causal that cannot be thought away without the success also ceasing to exist (conditio sine qua non). The success therefore does not occur in the absence of the cause.
Illegality
Finally, liability exists in principle only for unlawfully inflicted damage.
The duty of care
The liability of the animal owner for damage caused by his animal is extraordinarily strict. In particular, the owners of potentially dangerous dogs are advised to take out private liability insurance.
In order to be exempt from animal owner liability, the animal owner must be able to prove that he/she did everything necessary to avoid the occurrence of the damage.