m0useanswered grow question 2y ago Do u have pets?? kinda looks like a bite mark and follows a curve like the side of a mouth.
Could have been a pest but looks a bit different from one that resembles damage like that. leaf miners.
If it does not progress and no new damage is happening its a write off and nothing to over think. I think it looks like some sort of environmental damage via a pet or pinching/pulling on something.
Good Luck!