@wackowax ,Waqas, If port is found to be bad/loose/damaged , this is really not a repair for the inexperienced because the charge port for your device is soldered to the mother board and the heat generated could cause further damage if not very careful. I will post a link to a tear down guide/vid. to get you inside the Nintendo Classic Mini NES to check the charge port and will also post a link(not your device) showing what is involved in repairing a mini USB attached to the board. You can do a search for replacement port or you may have to try visually matching it up(may be standard type). If not wanting to attempt the repair have a couple good local game/computer repair shops have a look and estimate repair. Good luck. I hope this helped you out, if so let me know by pressing the helpful button.
http://www.theverge.com/2016/11/13/13614434/nes-classic-edition-teardown-nintendo
https://www.youtube.com/watch?v=Ov-HACi975w