While my car was parked, it got scratched on the front right-hand side.
The front right-hand side of my car got scratched while it was parked.
While my car was parked, someone scratched it on the front right-hand side.
英語で「車を停めていたら、前方右を誰かに擦られてしまった」は「While my car was parked, it got scratched on the front right-hand side.」又は「While my car was parked, someone scratched it on the front right-hand side.」と訳せます。「Got scratched」の例の方は受身形ですが、「got」は、「～られてしまった」のニャンスを強調します。
車を停める = park the car
誰か = someone
前方右 = front right-hand side
擦られた = was scratched
While my car was parked in the carpark, someone bumped into the front right-hand side of it, leaving a scratch.
When my car was parked up, somebody hit the front right-hand side and left a scratch.
The front right-hand side of my car was hit when the car was parked up.
My car was parked up legally, but somebody hit my car and damaged the front right-hand side.
Right-hand side = On the right
The front end of a car can sometimes be referred to as the "nose".
The cover which goes over the engine is known as a "bonnet" in British English, and a "hood" in American English.
You can specify that the car was parked up in a legal parking spot (i.e, a parking lot) but it is not necessary if that information was already spoken about. I would assume that the main information of this point is that the car was hit when it wasn't being driven, and also where on the car body it was hit.