As per the title: I've had my bike serviced by a bike shop, who helpfully tightened up the stem cap and pinch bolts on my headset. I rode it approx 15 km (9 miles) and I noticed some play in the headset was reintroduced. I went through the usual steps of tightening it again (loosening off the pinch bolts, then checking wheel/bar alignment, then tightening the cap bolt, then re-tightening the pinch bolts), however I noticed the ridiculous amount of tightening on the pinch bolts. So much so, I could barely remove the bolts and nearly rounded them off.
I'm concerned that there's some damage to the steerer tube, as the pinch bolts were only rated to 5NM and they were clearly much tighter than that, and the play in the headset had returned in a short distance. Attached are some photos of the tube, where I can't see any obvious cracks, but you can see where the stem has been tightly mounted. (The top section that is dark, with an oval imprint, is where the stem has been mounted very tightly).
Without returning to the shop that bungled the job, is there a way to tell if this is safe to ride?