As others have said, there’s the UDRP, which is what the GoDaddy-linked answer is covering, but here’s from ICANN (the source, mentioned in GoDaddy’s policy):
https://www.icann.org/resources/pages/help/dndr/udrp-enWithout knowing if his was for a business, or a service mark or trademark, or even some just-well-known name, AND without knowing your location, it’s hard to say more. In the US you could (IaNaL) pursue small claims court, at the cheapest, and try to make an argument that they registered it in bad faith; if they fail to show up I’d guess an order from the court to transfer the domain back to you in exchange for compensating the purchaser for a year of registration would be your best possible (but who-knows how likely; courts are fickle things) outcome.
Outside the US, your local laws might be nicer to you legally.
