This is an odd situation. The knock point is 10. A player knocks in error. The player then shows..

This is an odd situation. The knock point is 10. A player knocks in error. The player then shows a stead if three cards, say three 10s and show a run of four cards. After his discard, the player holds an 8, a 3 and a 2 for a total of 13 points. The player then draws the fourth 10 from the stack pile. Is the player required to play his 10, discard the 8 and drop for 5 points? Or, may the player discard the, either by accident or on purpose, and play on with 13 points?