it could be a lot of problems. he will most likely lpse the tip though. im sorry. it could have been shed. it could also be due to the fact that a tankmate is overagressive. im not saying it has any, but if it does id try seperating them for a little while. my females get quite nippy at my males when they wanna have too much fun. it could also be crickets. ive seen crickets chew up lizards tails pretty bad. they even got my niger uromastyx's tail from 2 spikes up. i was real mad at that.. but hes ok, so all is good. it could have also been the cover be3ing shut on it, or a rock or other heavy tank ornament catching it. the causes are endless on cases like that.