Congratulations on your new title. Now, fight this knockout machine.

That’s what the IBF effectively said on Thursday, ordering its new junior lightweight titleholder Anthony Cacace of Northern Ireland to immediately begin negotiations with his mandatory title contender, Eduardo Nunez.

The Matchroom-promoted Nunez (26-1, 26 KOs), of Mexico, is coming off a second-round TKO of former featherweight title contender Oscar Escandon on Oct. 28, and was already the mandatory for former titleholder Joe Cordina, before Cordina was stopped in the eighth round by Cacace on Saturday on the Oleksandr Usyk-Tyson Fury card in Saudi Arabia.

Cacace (22-1, 8 KOs) “inherits the mandatory obligation of the previous champion … which states that should the title [change] hands as a result of a voluntary defense, then the new champion shall inherit the mandatory obligation and must defend within the time remaining for the champion from whom he won the title,” the IBF Champions Chairman Carlos Ortiz Jr. wrote to Cacace promoter Queensberry.

Ortiz wrote that negotiations should be concluded by June 22, and if an agreement cannot be made by then, the IBF will conduct a purse bid.

He attached an IBF rule stating that “a champion’s failure to comply with this obligation will be sufficient cause to have the championships committee and board of directors consider withdrawing recognition of the title.”

Cacace, 35, enjoyed a hero’s homecoming this week, and now he has to move on to the sobering business of the sport and a likely matchup against a relentless power puncher yearning to take the prize he just so recently collected.