I was going to say a sebaceous cyst maybe? Neb had one on one of his paws that eventually disappeared/sloughed off. But there's a few things it could be.
Neb, Beagle mix, born April 2008
Xerxes, Beagle, born 2016
RIP Luc, German Shepherd mix, July 2003-December 2018
Timothy and Cordelia, kitty cat terrors!