Hi, my new monstera leaves were a bit dirty so I wiped them with a wet cloth and then this strange marking appeared overnight,any idea what caused it?

[Beastlybirch]

 

[Marck]

This looks like plant oedema (or edema). Oedema is a physiological reaction in which water enters a plant's cells quicker than ot can exit causing the cells to burst. Oedema is not serious unless it happens constantly. The causes of Oedema are somewhat idiopathic. Often a very abrupt change in temperature, humidity, or light level will cause it. Wiping your plant might have somehow triggered the oedema, but it might also be coincidental.