You should be fine.... mainly since your corrected the problem quickly.
Be thankful it wasn't the other way around. My father did the reverse at a local station. The fuel delivery truck dumped diesel into the premium tank. When dad filled up with premium and drove off, he got about 1/2 mile before the engine gave way. The worst part was, the truck was a new Silverado with a Northstar engine. Needless to say, the gas station bought a new Northstar!
Keep smilin'..... hopefully there was no damage that a filter change won't cure.
76 240D (W115) - 555K miles
78 300D (W123) - 200K+ miles -- SOLD