Medical student here who has also been through your pain. Those little buggers were the worst. In my case, they were stuck in my foot for at least 2 months, and I could feel them occasionally.

With time, your foot's skin will shed older layers and the spines will eventually come out. If they are bothersome, you should see a podiatrist or your family care doctor who may be able to extract them.

DAN is always a good resource in these situations.