Before the age of electronic monitoring knocking was caused by :-
1.Using lower octane fuel than was recommended by the engine maker especially under higher loads.
2.A hot spot in the combustion area causing the fuel to ignite before the spark plug fired caused by poor manufacturing ( thin edges becoming red hot) or excess carbon build up ( also becoming hot).
3.Incorrect early spark timing.
4. A leaner mixture causing higher combustion temps.
I cannot see it doing any damage over a short period.
The question is ...what caused it & how can the problem be rectified. Hopefully the engine management system can be 'tweeked' by the dealer.
Good luck.