It's your choice BobbyBobBob. If your error is a serious one e.g. it's not the correct model number, or found it doesn't actually work, when you've said it does work, then you can either add the correction (very clearly) by revising the description, or you can end the auction early and relist it with the correct description. If you've paid a listing fee, then that's gone.
If someone has made a bid, you can add to the description but advise those bidders to contact you if they wish to withdraw their bid in the light of the new information. Not in ideal scenario. Best probably to just end early, the bidder might be put out, but you won't be charged an extra fee; just a possible listing fee again. Good luck with what you decide.