The general rule is that the statute of limitations for these types of charges is several years.  However, criminal charges can only be "pressed" by the police.  As a private citizen, all one can do is report criminal activity to the police -- it is then up to them to decide whether or not to charge the suspect.  The longer that one waits to report criminal activity, the less likely it will be that the officers will take the report seriously and investigate thoroughly to culminate in an arrest.  In any event, however, if you feel that you may be subject to criminal charges, I suggest that you consult with and/or hire a local attorney.  If you are contacted by the police prior to consulting with an attorney, simply refuse to answer any substantive questions without an attorney present -- and then hire an attorney, asap.