If you accidentally inhale bleach fumes you need to get yourself outside into fresh air right away if possible.
If you've just inhaled the bleach fumes alone then there's usually no need for seeking medical attention and usually just breathing in fresh air is good enough.
But if you do accidentally mix bleach with other chemicals such as ammonia then you do need to get fresh air as well as seek medical attention because ammonia and bleach creates a deadly gas.
So do not under any circumstances mix ammonia and bleach or any other chemicals together as it can be deadly.