Good point on the oil pressure being higher than the cooling system. I was thinking of the crankcase/sump minimal pressure but forgot that there has to be oil pumped up to the valve gear through the head.

Some people on other engines have had success eliminating head gasket leaks by retorquing the head bolts. Don't know whether this would work on an MB diesel or not.

As has been mentioned, you probably just want to keep an eye on the fluids for contamination and continue to drive. Maybe the next time you have the valve cover off to adjust the valves, you can retorque the head bolts. They do get torqued in a specific pattern.

Ken