Yes, you can get blood blisters, or even broken bones depending on how large/strong the magnets are and what falls between them. But accidents aside, the worst part is when you're showing someone else and you tell them that they are VERY strong--unexpectedly strong in fact--and they STILL underestimate the strength, and you hear the inevitable "clack" of the two magnets sticking together, and hope that neither has cracked. I would suggest dipping larger rare earth magnets in that plastic tool goop so they have some padding.
These kinds of magnets are found in hard drives, albeit the hard drive magnets are much larger than these puny disc magnets. Keep them away from CRT televisions and monitors, though you can see the screen discolor when you do bring them near.
For children, a greater danger than broken bones or pinched fingers is if they swallow the magnets. One can go into the intestine and then connect with another and rip through the intestinal tracts. It was one reason many of those toys from China were recalled.
