You can't charge a laptop via USB. Unfortunately, a lose power cord generally means that the port is lose on the motherboard and fixing it usually involves a costly replacement but in this case, it's likely your only option.
Yeah, you'll need someone to open the laptop up and either re-glue the socket into place or replace it. If the socket's physically worn out, you might need to replace it. A local computer shop should be able to order and fit a replacement socket if that's the case.
The power plug is usually separate to the motherboard and easily swapped out once the laptop is open. A shop should be able to do this for well under $150 for parts and labour.