You caused the damage. Much as if you had crashed into another vehicle while driving, YOU are responsible. Your actions / negligence has caused this.

You have 2 choices : either you pay for the repairs directly, or inform your insurance company, and they pay.

Either way, you MUST inform your insurance company of it. Failure to do so would be a breach of your insurance terms and conditions, and your insurance company (if they found out) could cancel your policy on the spot. The reason for this is that you may be a higher risk than you have made out, and they've no idea if you've tried/done this in the past.

Do be advised that having insurance cancelled is not a laughing matter. You would find it VERY hard to get other insurance, and would probably have to pay large amounts (again, you are viewed as high risk/potential fraudster)

Got to agree with others Tomthetiler, you made the mistake, albeit innocently, but it is you who needs to rectify the mistake. That means doing the right thing and paying up, apologising and coming out of this looking like a decent citizen. A poorer but wiser man.

Cheers Concrete