If your bank gave you credit for a check that is found to be fraudulent, the bank can reverse the funds from your account. As the payee of the fraudulent check, you must pursue the maker of the check if you wish to seek reimbursement.
Two tips: Never accept a check from someone you don't know, especially if the person wants you to send some of the funds to a third party. Be cautious with any offer that asks you to pay for a prize or gift.
Learn more on the Report a Fraud/Scam page.