For the protest to be successful you will have had to protest under the racing rules. If you did not protest on the water at the earliest opportunity and fill in the form etc under the racing rules afterwards you will not be able to protest. 

The short answer is that if you believe another boat broke a rule you should protest, damage or no. And if there’s contact almost certainly someone broke a rule.

Damage liability is separate from penalties under the racing rules, it’s between you, the other owner and your respective insurance companies. In the US we have prescriptions saying that accepting a penalty does not constitute accepting liability for damage and that protest committees shall not adjudicate damages.

Sometimes insurance companies would like to know the results of a protest hearing if there was one to help them assign responsibility for damage.

It is a pet peeve of mine (and I have many peeves), that insurance companies actually WANT you to go through the protest procedure in many cases. This wastes the PC's time if not needed for race purposes and often causes fairly large amounts of money to turn on, shall we say, less than formal procedures in many cases.  It has occurred to me that some sort of arbitration panel, separate from the race's PC, for cases that are purely for insurance purposes, would be a sensible approach. That panel could work at its own pace and even get paid!

Michael, it seems to me that in the absence of a protest committee decision an insurance company could work out the RRS situation themselves and figure out which boat broke a racing rule, just as they would if it were an IRPCAS situation. They could easily hire a certified judge as an expert witness.

My concern in these situations is that a less than rigorous PC might be tempted to be “flexible” about validity because they think the parties “really need a decision.”

Well, there might be a benefit to having a regularized system, and one which has some authority to collect needed information. Second, if we DO believe that liability between racers should be allocated based on RRS violation (and that's not a certainty), then a system that has some insight into the RRS is a good thing. Finally, if the damage is less than the insurance deductible, or one party is not insured, then we'd want to avoid an imbalance or just a "who can shout louder" situation.  This is all hypothetical.

One of the easiest solutions to avoid the consequences of tbe US  prescription is to have the person in charge sign the protest form "Retired in acknowlment of breaking rule xxxx. Damage was the result.  Or something similar.
But first, you must protest!
I might also add, just because a boat has retired and cannot be further penalized, does not mean it cannot be heard.  In fact, a PC must hear all valid protests filed.  True,  a protest may be withdrawn, but that has to be requested by the protestor 

Without commenting on anything else, at least in English law, to make an admission as Leo suggests, is very dangerous and most insurance companies would go wild if you did.  Their rules tell you never to admit that you were in the wrong in motor accidents or sailing ones.
Again in England I think the question of insurance liability and whether there's been a breach of the rules are two separate questions.  They often run together but they have to be looked at with separate eyes (or brains!)

David, it’s definitely a jurisdictional issue. Here in the US we have a series of prescriptions which address this directly.  Here they are below:

US Prescriptions to RRS 67
US Sailing prescribes that:

In the US, the kicker is (c)’s, “..a boat agrees that responsibility for damages arising from any breach of the rules shall be based on fault as determined by application of the rule….”

… and that of course is what a protest decision gets them, normally with the right to appeal that decision if they disagree.