The 21-year-old, who scored once in 51 appearances for the Pilgrims, has been on loan at Bower Fold since November.
His solitary United goal was the stunning 25-yard match-winner at Brackley Town on August 12.
As part of the transfer agreement, Galinski will not be eligible to play against United when the sides meet on April 11.
Galinski moves on with the best wishes of everybody at Boston United.