When Does a Player's Turn End
As far as the game is concerned, you have ended your turn and the next player has been instructed to take theirs.[1] And since the rules say take-backsies are only allowed if... Wait a sec, there are no rules concerning take-backsies in Ticket to Ride. In fact, I've never see a game that allows take-backsies.
It doesn't mean you can't take back the move, but how that works is something your group will have to decide. Personally, I have absolutely no problem with allowing the change since nothing was done based on the move that was performed. But this is my opinion. What your group allows/tolerates is up your group's business.


One of the expansions has an optional second action you can take. So, in that game, you may not have ended your turn.