Does sending a message to the police later, expressing a desire to cover material costs without admitting guilt, along with seeking forgiveness and feeling remorse, mitigate the sin of lying and denial in a car accident?

We ask Allah to accept your repentance. You have done well by taking financial responsibility for the accident, and this significantly alleviates the sin of not acknowledging the truth. However, if the car owner suffered any other moral or material damage, you must seek his forgiveness or compensate him, because one of the conditions for repentance related to human beings is to absolve oneself of the wronged party's right by seeking their absolution or restoring their right to them.