Yeah, it is generally advised that you feed your gecko insects no bigger than his head. The gecko likely has the upper hand when you put them in there, so just make sure not to leave them for too long, especially when the gecko’s sleeping because he is vulnerable then.
UPDATE— so I tried a morio worm they were quite big, he ate one and seemed like he struggled to swallow. I left him for 5 mins and tried again but he kept turning his head away so that’s a no no
I only started feeding mine morio worms when they were a year old. would not suggest moire worms at that age. they can be pretty big and will be hard to chew.