Bad sheds can dry, constrict, and cut off blood circulation from any part of the gecko's body over time. This is especially a problem with toes and tails. There is nothing that can be done now for him; he will never have toes on that foot again - they've "died" and fallen off.
If you raised him yourself I would suggest being a lot more vigilant in inspecting the gecko after each shed and making sure he has access to a moist hide if he doesn't already. This sort of thing can be completely prevented by proper gecko care.
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0.1 Albino Leo Gecko
0.1 Crested Gecko
1.0 Dear Boyfriend
Departed: Harvey and Spock