Perhaps feeling flush after selling a 51 percent stake in his Barstool Sports to the Chernin Group, the website’s founder, Dave Portnoy, has purchased a $2?million house on Nantucket. The transaction, which took place last fall, was first reported by Housely.com. Portnoy, who calls himself “El Presidente,’’ plunked down his hard-earned dough on a pad described by Zillow as a “tastefully landscaped 4-plus bedroom home with in-ground pool, blue stone patio and deck on an open acre of land [abutting] over 30 acres of Nantucket Land Bank property . . . located at the end of a cul-de-sac in a quiet neighborhood close to Cisco Beach, Bartlett’s Farm and town.’’ When the deal with Peter Chernin was announced, Portnoy said the Barstool staff would be moving to Manhattan. It appears he’ll be back from time to time.