This has reminded me of the time my son [aged 2 at the time] bit my bum.
He'd been watching Noddy and Bumpy dog bit one of the goblins as he tried to steal Noddy's car, so he thought he'd re-inact the scene on my behind.
I was in total shock and my kneejerk reaction was to smack him
The good news is 7 years later the teeth marks have gone and my son has no recollection of the event at all, no trauma at having been smacked, no self-esteem issues, nothing.
Harman, you're a normal mum doing the best you can. Try not to dwell on isolated instances like this and hide all potential stabbing instruments well away.