Been expressing milk out using electric pump, and now that my nipples seems to be painful and sore even when lightly touch. Any mummies have any ideas how can I reduce the pain?

On top of what the abovementioned mommies have suggested, perhaps you can consider using lanolin or any other similar product to soothe irritated skin as well as also allow for a better suction, smooth gliding, and minimal friction while pumping. The friction could be the cause of that pain you've described and lanolin could help alleviate the pain.

are you using a high level to pump out your milk? it could hurt your nips if the power is too high.. higher level doesn't mean more yield..

Check if flange size is correct?