You can try putting a card into to the PCI-express slot and see if the card performs correctly. The fact that your PC still works probably means that you didnt damage your bus or your motherboard.
But, it is impossible to say really without professional diagnostic tools. Motherboards are not really feasible to repair and manufacturers just tend to throw them away if something is broken or recycle for parts.
Try if the slot works and if you are lucky you wont get intermittent problems in the future.
You must always power your PC down/unplug when working inside it. You could risk touching a fan, shorting something or even getting electrocuted.
It is even advisable to let the PC sit for a few minutes to get the charge out of most parts, but capacitors can still shock hours after that so you must be careful what you touch.