Is Punctured Hole On Palm With Red And Black Strings After Digging It Concerning?

my son works in a meat department in a store. he grabbed a bunch of crab legs and one punctured a hole in his palm. his hands were dry from wash a lot at his job. we took him to a dr. and he gave him some cream and told him to quit digging in the hole. he tired for 2 weeks and the dryness went away but hole was still there. he dug it out again and with tweezers puled red and black strings out. now it has healed over. he just told me this. what could it have been and are there any test he should get.