Here is the offense:
21802. (a) The driver of any vehicle approaching a stop sign at the entrance to, or within, an intersection shall stop as required by Section 22450. The driver shall then yield the right-of-way to any vehicles which have approached from another highway, or which are approaching so closely as to constitute an immediate hazard, and shall continue to yield the right-of-way to those vehicles until he or she can proceed with reasonable safety.
Without knowing why the officer thought you proceeded without properly yielding, I can't say if you have a good argument or not. If there were any approaching vehicle that had to brake or otherwise were impacted by your pulling into traffic from the stop sign, then you may lose. You may have to seek the officer's notes through discovery to see if you can get an idea what he might say if you go to trial.