Can it be fixed after putting a game in wrong?

Yes that can be fixed. You can fix it yourself if you have moderate soldering skills. You will need to remove the motherboard. A guide for doing that is here. Then you will need to remove and replace the game card reader. The game card reader is soldered on to the motherboard. The bad one will need desoldered and the new one will need soldered on. Then reassemble by reversing the steps in the fore mentioned guide. eBay is a good place to acquire the new card reader part. Here is 1 from there sold by a US seller. Here is one from Hong Kong at a cheaper price.