After a goalless first half, the Pilgrims trailed to Montel Gibson's 56th minute opener - but Obiero and strike partner Jaanai Gordon turned the tables in the 59th and 61st minutes.
Gibson subsequently went on to complete his hat-trick with two late goals to hand Ilkeston victory - against a United side fielding a trialist in goal, with Sam Long and Rhys Davies both missing out through injury.
Boston (3-4-1-2): Trialist A; Ben Pollock, Lebrun Mbeka, Trialist B (Luke Shiels 46); Keenan Ferguson, Tom Platt, Tom Solanke, Alex Brown (Trialist D 46); Scott Pollock (Jordon Crawford 46); Micah Obiero (Jake Wright 77), Trialist C (Jaanai Gordon 46). Sub (not used): Ellis Myles.
Referee: Harry Jones.
Attendance: 286.
PIC: Russell Dossett.