40 Waltham St., BostonHome to artists and restaurateurs alike, the SoWa (South of Washington) district of Boston’s South End has transformed from an area once known for mills and warehouses to a mecca of modern creativity, attracting small businesses and their customers for the past decade. One such addition to this thriving neighborhood: M. Flynn Accessories, a 5-year-old boutique owned by sisters Moria and Megan Flynn. Inside the bright white showroom, M. Flynn boasts a mix of fine estate jewelry, customized pieces, and guest lines at what Megan calls “a giftable price point.” The scent of freshly cut flowers and Tocca candles fills the air, and colorful candy jars of Smarties and Ring Pops create a refreshingly playful atmosphere.SERENDIPITYIt’s hard to believe the sisters were once ­wholesaling out of the second bedroom of Moria’s apartment and wondering if they’d ever g