Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
Given that the camera was dropped, the repairs will have to be paid for in full - warranty is voided by that means, I think.
As for determining the repair cost for this problem, you would have to ask a Nikon Repair facility or shop about that. Specifically, contact them, describe the problem and the model #, and ask for an estimate on repair charges.
If you would like to contact a Nikon repair shop in your region, please let me know your region by zip code, or by town/city and state, and I will advise you further.