Hi Chama Chhakchhuak. Unfortunately by opening the HDD you've probably voided its warranty (assuming it still had any left). Your data is not necessarily lost. But I suggest you don't try anything else yourself and go for a professional solution such a as a data recovery company if your files are important to you. There's no guarantee on how much of your information they will be able to retrieve, but at least it's worth the shot. I know this is a bit late considering this case, but I would suggest that in the future you always keep a backup on an external drive with your most important data.
Hope that helps. Let me know if you have any questions.
Good luck,
Boogieman_WD