Upon general recommendation (read: peer pressure), I went to an orthopedist this morning to have my knocked chest checked out by a professional. For some peace of mind I guess 10€ Praxisgebühr (with Krankenversicherung) is cheap enough, even for a cursory inspection?
A nurse took two X-rays, which I didn't get to see, and a doctor briefly listened at my chest and barely at what I had to say or ask, concluding nothing to be broken nor ripped. The bruised spot just needing time to heal by itself, no need for any suggested supportive bandage nor unasked-for painkillers.
I'm even allowed to practice any sportive activity, as far as possible, and should be alright for some unusual diving in a few weeks time :o)