Dina,
You might want to check with the manufacturer of your car seat, but more recent articles that I've seen actually say that you don't necessarily have to replace a car seat after a minor crash. I'm sure there is more information out there, but here's information from one article I found on parenting.com:
When Your Car Seat's Been In a Crash
What to do if your infant seat has been in an accident
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By the editors of Babytalk
One of the cardinal rules about car seats has always been to replace a model that's been in a crash. Now, thanks to the constantly improving quality of today's seats, that has changed. Recent studies have shown that child safety seats can withstand the impact of a minor crash without affecting their future performance, says National Highway Traffic Safety Administration spokesperson Eric Bolton. How can you tell if your crash was minor? It must meet all the following criteria:
You were able to drive your car away from the scene of the crash.
The vehicle door closest to the child safety seat was not damaged.
There were no injuries to any of the occupants of your vehicle.
The vehicle's air bags did not deploy.
There is no visible damage to the car safety seat itself.
If you're still unsure, take your car seat to an authorized inspection station for free advice. (Find one near you at nhtsa.gov.) Need to replace a damaged car seat? Talk to your insurance agent; some policies will cover the cost of a replacement seat.