Blood circulation is one of the biggest issues with nipple play and using clamps. Usually clamps should not be used more than 10 to 20 minutes at a time.
I remember a guy writing to the forums years ago. He'd played with a lady who really didn't know what she was doing. She left clamps on his nipples for a couple hours. He was writing to find out if there was any chance he'd regain any sensitivity to his once very sensitive nipples. It had been 6 months since he'd played with this lady just the once. Sadly the nerve damage was most likely permanent.
OP - if what is being done to you involves broken skin/flesh, there would be the possibility of scar tissue. And scar tissue has less nerve endings that regular tissue. Just a thought.
and just about anything done to breasts/nipples could result in damage/loss of sensitivity. You need to weight the benefits with the risks. Much as in life.