Apple seeds from apples release small amounts of cyanide when chewed and digested which could kill you if you ate too many of them.
However if you swallow a few apple seeds the apple seeds are not gonna harm you.
I've eaten a few apple seeds before as a kid and never gotten sick from them.
You'd have to eat and chew at least 85 or so apple seeds for the cyanide poisoning to happen to you.
I would not recommend eating apple seeds but a few are not gonna harm you.
Just don't eat too many apple seeds and you'll be fine.
Cyanide in a large enough dose can be deadly quickly as it can stop you from breathing.