Back sore but that is nothing new. Knees bruised slightly. Not too bad.
Just for fun, document your brusies. Take photos with a copy of today's newspaper showing the date, next to your knees. Much better would be to go to the hospital, where you will get an actual exam and diagnosis.
The hospital or your PCP will likely provide some medications for pain and refer you to a physical therapist or chiropractor.
Here is your chance, if nothing else, to get treatment for your sore back at the cost of the negligent party. If you are so inclined, you could treat for three or four months, and with little more effort than hiring an attorney and giving him a third of any settlement, you could easily wind up with anywhere from five to ten thousand dollars in your pocket. And possible an improved back. You could even pursue a bodily injury claim by yourself, no lawyer needed, and perhaps do better.
I'm not advocating advancing a fraudulent claim, but bruises are contusions and can't be faked.
I work as a fraud investigator in an insurance company's Special Investigative Unit. I handle cases where people are getting settlements for accidents in which there are NO physical damages and NO visible or objective injuries. Why? Because there is virtually no way to prove that someone did not sustain a soft tissue injury in a motor vehicle collision.
I understand your reluctance to make a big deal out of this incident, and your aversion to lawyers, but the system is in place to compensate you for an event that was none of your making and to penalize the party whose negligence caused you harm. Use it!