I got poked by the same type of urchin about 2 months ago. The end of the spine broke off in my finger. It took about 2 weeks for my body to get rid of it - just like any other sliver. My finger was tender for a good month, but you should be fine. Swelling around the area after a day or so will likely indicate (did with me) that the tip of the spine is still there. I dug around with a needle and fished it out (the oral dosing of alocohol will likely help with that process)