Oil leak on passenger side?

Oil leak on passenger side top of valve cover.

My car mechanic advised me  ..............

This is due to a damaged gasket on the valve door and so it is necessary that the gasket is changed immediately.
Try and tighten the bolts on the valve door so as to confirm if this will close the leak.

I tightened the bolts and this helped to stop the leak.At present problem is solved.