Dear Alok,
Prima facie it is found his certificate is fake one, then pursue proper procedure under your Standing orders or your Conduct & Disciplinary Rules, if any. Nevertheless -
1. Suspend him pending inquiry and issue him a simple charge sheet asking him to show cause why he should not be dismissed for submitting fake certificate to secure the employment. Give him the shortest time, say 7 days or 10 days to reply in writing to SCN together with genuine certificate, if any, appoint an Enquiry Officer to proceed with this. Based on his reply do the needful. Remember you have to pay him Subsistance allw. during the suspension period.
Reg.salary for the months worked, if it is a statutory or skilled post which requires a competency certificate holder only can be employed you may even forfiet his salary after following above procedure. Otherwise just pay him, decide the rest as per the enquiry report.
Natural justice should prevail.
Rgds.