The South Korean hit the woodwork twice in the first half as Spurs somehow failed to build on Lucas Moura’s opening goal.
Son was replaced at half-time by Steven Bergwijn and Spurs lost much of their impetus as Newcastle gained a foothold in the game.
Nevertheless, Jose Mourinho’s side looked on course for all three points until Newcastle were awarded a controversial penalty in the 95th minute after a VAR review showed Eric Dier handled in the box.
Callum Wilson slotted home from 12 yards to give Newcastle a share of the spoils and the bad news didn’t end there with Mourinho admitting afterwards that Son is set for a spell out of the side.
‘It’s an injury. We’ll have him out for a while. It’s his hamstring,’ said Mourinho.
Asked if Son is expected to be out for a ‘long’ time, Mourinho replied: ‘Yes’.
Spurs face a hectic week before the international break, with Mourinho furious that his side have to play four matches in seven days.
Tottenham take on Chelsea in the EFL cup on Tuesday before a must-win Europa League qualifier against Maccabi Hafia just 48 hours later.
Mourinho’s side then take on Manchester United at Old Trafford next Sunday before the international break and Son is not expected to return until at least October.