I think onions smell nice and want to bite into one
Do you think it'll taste good to bite into an onion?
I don't know, but I like the smell.
If you like the smell of onions and think you'd enjoy eating one raw then I think you should do it. You're allowed to eat whatever you want, and there is nothing unhealthy about biting into an onion.
I tried, I couldn't bite into it
At least you fulfilled that curiosity.   There is no reason to make yourself do it if you were uncomfortable with it.