Use care and critical judgement at all times. The human body is damaged by the flow of current through it. Tissue damage occurs via heating, just like a burn. More importantly, significant body functions such as heart beat and breathing can be affected by electrical shock. Circuits that operate with higher supply voltages should be treated with more care.
Wet skin has a much lower resistance than dry skin.
Blood, having a saline component, is quite a good conductor. Accidental shock via an open wound is quite possible, and could be quite dangerous. Metal jewelry is a very good conductor. If you have a power supply that can deliver high current, your class ring would be happy to provide the conduction path. Here the danger is heat rather than shock.