Two player competition. Player one miscounted her hand points, and moved her peg. As player two was counting her hand points, player one realized her error and wanted to add the discovered points. Was it too late? Did player two have a valid objection ? ( No muggins)
8.3 Pegging Incorrectly to the Player's DisadvantageIf the wrong number of points is pegged to the pegger's disadvantage (ie underpegging a forward score or overpegging a backward penalty), a correction is not permitted after the player's fingers are removed from the peg.
However, these are tournament rules. If you are choosing to not play Muggins, I recommend that all irregularities be treated more generously than in these rules. A good guideline for this might be:
If it is reasonably possible to restore the correct game state, then such corrections are allowed. Usually this means "before the next hand has been commenced by initiating the deal for it; and before the game has ended by a correct peg into the final hole."
Either agree to play cut-throat, with muggins; or play generously all round.
Finally - you claim this to be "Tournament Play". If so, why are there no judges appointed to adjudicate according to the official tournament rules? Your claim there seems dubious.