|This sounds like a laptop....|
A component could have broken.
A connector could have become dislodged.
Your CMOS 'coin' battery could have popped out of it's socket.
Your battery's internal contacts or connections could have broke (try with power cord but without the battery inserted).
Most of these require opening the laptop to verify and diagnose and most will not do this so you may want to bring it in for service. If this is under warranty, you might consider not telling them it was dropped (at least at first) since this may at least save you a fee for opening and evaluating the problem. If it becomes obvious the problem is from dropping you will need to pay for the repair, but you will not need to pay up front before you know the problem or the cost.
You have to be a little bit crazy to keep you from going insane.