Do I have to repair my car after an insurance claim?

Yes of course , to return your car to it's value before the loss and maintain your insurance policy sum insured as it is without any reduction. i.e to keep your property or interest value as it is in your current insurance policy .

Thanking you.

No, but if you receive an indemnification for it, it will be deducted from the next claim. 

For instance, if your car worth 50,000 and you have a coverage on it with a deductible of 1.000, after you get in an accident and you receive 11,000 on the appraisal, you will get 10,000 on a check. 

On the second claim "if you didn't repair the damages", if you get 20,000 on the appraisal, and deduct the deductible of 1,000, you will receive a check of 8,000.