The Colombia international was brought on for his debut in the second half of Sunday's 3-1 FA Cup win over Cardiff City and made an immediate impact with an assist for Takumi Minamino's strike on the day.
However, Diaz then went down clutching his knee in a worrying sight for the home crowd, but fears were quelled when it was revealed that Cardiff's Aden Flint landed with his studs on the Colombian's leg.
Klopp also allayed concerns of a serious injury after the game, telling ITV: "Now it's just a bruise and a little cut, everybody told him 'Welcome to England!'. There will be a scar so he remembers the first game but all good."
The Liverpool boss also paid tribute to returning teenager Harvey Elliott, describing the 18-year-old as "fearless" after he scored his first goal for the club after nearly five months out with an ankle injury.