The incident occurred in the second half at Portsmouth's ground when Bielik went to retrieve the ball from a stand packed with Pompey supporters.
Video footage showed Poland centre-half Bielik becoming involved in an altercation with a teenage boy, who caught the ball and then appeared to be pushed in the throat by the Cardiff player after he had thrown it back towards the pitch.
Hampshire Police launched an investigation following the match but took no further action after concluding their enquiries.
"Krystian Bielik has been suspended for two matches and fined £10,000 for misconduct during Cardiff City's EFL (English Football League) Championship match against Portsmouth on Saturday 5 September," England's governing Football Association said Tuesday.
"Krystian Bielik subsequently admitted the charge. An independent regulatory commission imposed these sanctions following a hearing."