Jack Mason's first half strike for the Lions was cancelled out by Owen Sheriff's 80th minute equaliser.
The result extended United's unbeaten run on home turf to four matches.
Boston (3-4-2-1): Jake Lovelace; Oskar Rajski, Owen Sheriff, Taylor Jaine; JJ Ward, Rueben Fogg, Kyle Featherstone (Krisztian Gagyi 46), Josh Doran (Taylor Redman 71); Han Stevens, Jack Waddington; Flynn Slater. Sub (not used): Lucas Stubbs.
Referee: Alistair Wilson.