Suggest Remedies For Fiberglass Form The Cast Stuck In Skin

Hi. My son (9 yrs old) had a compound fracture in his left arm. He wore a big cast (that went above the elbow) for almost 6 weeks, then a short cast for 4 weeks, which was just removed yesterday. When the short cast was removed, we noticed that fiberglass threads from the short cast are now embedded in his skin. We can't pull it out because it hurts him. Will these fiberglass pieces come out when the old dead skin sloughs off over the course of the next couple of weeks? I'm a little concerned about possible infection or something bad like that because the fiberglass is a foreign object.