I would give them a call and ask, out of courtesy, if they have found any damage, if I were you.
Imho, best to get in touch with the other party & find out what their intentions are? 
I reckon a quick call as a courtesy would be the way I would go 
I would agree with all of the above - common courtesy demands nothing less. It’s also useful to assess the state of mind of the opposing party by initiating contact before things go much further.
The point about informing your own insurers is also well made - irrespective of whether or not a claim is subsequently made.
In seeking insurance a proposer is being invited to disclose any matter deemed by the insurers to be relevant to the cover being sought. While it's impossible to say whether or not details of this incident would ever see the light of day, should the opposing party not make a claim - and you don't declare them, there now seems to be a propensity for insurers to use any excuse at all to deny cover in the event of a future claim should you ever need to make one citing (in this case) non disclosure of relevant facts.
If you do decide to inform them (having spoken to the other party beforehand) I would do so as soon as possible.