Dreams involving sea creatures, like a sea urchin, can symbolize various aspects of your emotional state or current life situation. Sea urchins are often associated with protection due to their spiky exterior, which might suggest that you are feeling vulnerable or are in a situation where you need to protect yourself.
Holding the sea urchin in your left hand, which is often associated with receiving and intuition, may indicate that you are currently processing your emotions or are open to receiving insights related to your feelings. The fact that it spun and touched your arm without poking you could represent a situation in your life that feels risky or uncomfortable, but ultimately isn't harmful.
This dream might be encouraging you to explore your emotions more deeply and to confront any feelings of vulnerability with the understanding that you have the strength to handle them. Consider what aspects of your life right now feel prickly or defensive and how you might be able to engage with them without fear.