Tolley was beaten to the ball by Sam Purcicoe a few yards out following an inviting cross from Spriggs as Lynn looked to turn the screw.
Rainworth's Connor Higginson blazed over for the Wrens, who only named three substitutes on the bench for the game.
The deadlock was finally broken by Spriggs, from the penalty spot, in the 30th minute after Tolley robbed Ashley Kitchen of the ball before being brought down in the box by Goward.
Rainworth almost levelled matters three minutes later when Higginson's shot whistled past Danny Gay's post.
On the stroke of half-time, Beaumont volleyed over when well-placed in the box.
After a scrappy start to the second period, the first shot in anger came from Goward, whose free-kick flew over the woodwork.
Quigley's blockbuster was palmed away by the goalkeeper at the other end, but there was a lack of real excitement at either end of the pitch.
Twenty minutes from time a drab encounter was finally settled when George Thomson's cross was headed goalwards by Phil Gulliver and Watson pounced to hook the ball home.
Debutant Charlie Butt, who came on for the final 25 minutes, almost made it 3-0 but the youngster's shot flashed across the face of goal.
Blair Anderson and Higginson almost grabbed a consolation for Rainworth but their efforts were saved by Gay.
Former Linnet Mark Camm was an unused substitute for the Wrens after picking up a hamstring injury in midweek.
Lynn: Gay, Watson, Gulliver, Lee, Yong, Spriggs (Butt 65), Bunting, Quigley, Beaumont (Thomson 60), Tolley, Dunkley (Biles 85). Subs not used: Fryatt, White. Goal: Spriggs (pen 30), Watson (71).
Rainworth: Barcherini, Hanson, Goward, Purcicoe, Kitchen, Williams, Lloyd (Anderson 50), Hollis, Higginson, Holmes, Kimberley (Jenkins 72). Sub not used: Camm.
Referee: D. Stobbart. Attendance: 658. MoM: Jason Lee.
Report by permission of the Lynn News