Holland's 74th minute strike settled a tight encounter against Grantham Town at The Jakemans Stadium on Wednesday afternoon.
Holland, Jenson Bark and Arkadiusz Michalczyk all went close to extending United's advantage in the closing stages, but one goal ultimately proved enough.
Boston (4-2-3-1): Oliver Swaby; Jack Brown, Jack Withers, Taylor Gray, Callum Rodger; Peter Evison, Jordan Tate (Jack Henton 59); Marshall Young, Jenson Ball (Arkadiusz Michalczyk 75), Harrison Holland; Jenson Bark. Sub (not used): Seth Greeves (gk).