What happens if the owner of the forged check is not going to press charges but my friend wants to press charges on me since his account is negative?

That has several implications. First, if he forged a check, why would he want to try to press charges since he is implicating himself or is he just saying that you did it and tossing you under the bus? Second, if the authorities find out about this in whatever manner, the D.A. will likely prosecute, depending, perhaps on the amount stolen in the forged check. Third, how can you be sure the victim hasn't or won't file a police report? Have you discussed this with him and made a promise to return the money?