You need to pay your insurance company back for the money they actually spent. Whatever they negotiated off the doctor's original fee will not be your responsibility, you just make the HMO "whole" regarding actual cost to them.
The full cost of the bills will be taken into account when determining the settlement, and it's just used as one way of measuring how much treatment you required.
Just make sure that whatever you get, there will be enough to pay back the insurance company and have whatever amount you are looking for left over. Also, lawyer gets paid first and you have to pay the health insurance and everyone else out of the remaining 2/3.