A command that is blurted out, usually angrily, by one individual to another as a condemnation of the latter's behaviour, actions or poor choice of words. Those who indict another with such a phrase normally do so if the said individual has severely offended or insulted them, and are calling upon the individual to think about what they have done and atone for their lack of judgement.
Variations of this phrase, such as "Check yo self foo!" and "Check yo self before ya wreck yo self" are also used to communicate the same message: correct your behaviour (idiot/before you get in trouble)
Check yo self before ya wreck yo self. them shotgun bullets are bad fo' ya health!