You *CAN NOT* eliminate the error since you removed the questionable QSO from DXKeeper. LotW does not allow users to remove QSOs once uploaded.
+ You can eliminate the error in one of two ways:
1. Restore the QSO to your log so that it will "match" what LoTW reports when you invoke "Update from LoTW"; if the QSO didn't actually happen, set its "QSL Rcvd" item to 'I' so that it won't be considered for award progress.
+ or
2. Uncheck the "Report unmatched QSOs and QSLs as errors" on the "QSL Configuration" window's LoTW.
+ I recommend #1 so that you can keep "Report unmatched QSOs and QSLs as errors" checked
