dylokjai

I see smoke and smell burn oil from the cat on the passenger side engine bay. I recently changed my spark plugs but didn't see no leak from the valve cover or any oil on the driveway. But during the spark plug i did notice there was oil when i removed the last coil closes to the wall. can oil be coming out from that torx bolt hole? or was i suppose to put some kind of sealant on the thread before screwing it back on?