I'd at least have gotten a police (or highway patrol) report done.
Back in 2019, I was rear-ended in the "diamond" (HOV) lane in CA. At the time, I was driving an e-Golf (100% electric) in the HOV lane (sticker was still good) during morning commute time. Traffic starts to backup quickly so I slam on brakes (not engaging the anti-locks) as the red brake lights in front of me start approaching really fast. I am not in danger of hitting vehicles in front of me, but I look in my rear view mirror, and see a Honda Civic about to hit me. Since there was a shoulder to the left of the lane (wide enough to fit a vehicle), I swerved to the right (not hitting any vehicles in front of me or in the lane to my right), trying to give the Civic space on the shoulder to avoid collision. The driver doesn't avoid collision and damages my driver side rear quarter panel and left side of rear bumper. It was clearly the Civic driver's fault. He admitted it when we got out to exchange insurance info.
While waiting for CHP to arrive, I text a good friend who is a CHP officer. I ask him what I should do. He says get the other driver's insurance information at the very least. He said a highway patrolman's report isn't necessary if I don't want it since the other driver is admitting that he's at-fault. I get the Civic driver's insurance and contact info, give details to the CHP officer that arrived, but decline the report (since i was late for work).
A week goes by, and I'm contacted by the Civic driver's insurance company (The General), and they are claiming that I am fault, that I was in the lane to the right of the HOV lane and that I swerved into the HOV lane, causing their client to rear-end me. Had I agreed to the CHP report, I would've been good, but since I didn't, it was now my word against his. This was in May, and my lease was ending in early July.
I didn't file a claim with my insurance (State Farm) because I didn't want to deal with the hassle of it all. When I first leased the vehicle, I signed up for "Wear and Tear" protection. I paid an additional $500 over the life of the 36-month lease, and was covered for up to $10,000 in damages. The fine print was more specific, but when I turned in the car, luckily the lease inspector said I was covered and didn't owe anything.