I am afraid @raymills has not answered your question in the context of the game you were asking about - nine ball.
The exact wording of your original question is a bit confusing.
Can you sit after calling safety and make proper ball?
I will paraphrase to what I think you are asking, and show you the rules for that. Feel free to clarify if I got it wrong.
If you call "safety" before your shot, do the rules permit you to end your inning?
I will answer it, then point to the WPA rules which support that. The WPA is the official world governing body of pool. The BCA officially follows the World Pool-Billiard Association rule sets. When you go to various BCA websites, their rules all either link-to, or reference the WPA rules. My answer will follow those.
The answer is: When you declare a "safety", you execute your shot, and the inning is over, regardless of whether or not you pocket your called ball in the called pocket.
Supporting WPA rules (emphasis ours):
8.0 - Definitions Used in the Rules
8.17 Safety Shot
A shot is said to be a safety shot if the game in play is a call shot game and the shooter
declared the shot to the referee or his opponent to be a “safety” before the shot. Play passes to
the other player at the end of a safety shot.
The general rules apply in 9-ball, and this blurb from the general rules also shows that play always passes after a safety, no matter what.
1.0 GENERAL RULES
1.6 Standard Call Shot
In call shot games, the shooter may choose to call “safety” instead of a ball and pocket, and
then play passes to the opponent at the end of the shot.