Peterhead manager Jim McInally admitted poor game management cost them in their final match of the season.
Goals from Steven Boyd and Derek Lyle had put the Buchan outfit ahead after Jaime Wilson’s opener for the Sons.
But Morgyn Neill equalised with 10 minutes left and Wilson headed home an injury time winner.
Balmoor boss McInally said: “We should have done better, it was game management that cost us.
“It’s a lesson learned for some of the players, we were drawing 2-2 away from home so at that stage you take the point.
“We played well overall, first 20 minutes we looked like a team that had finished our season, but then we were spurred into action and I felt we were the better team after that.
“The biggest lesson to learn is at the end. We were playing away from home against a team that was really fired up and fighting for their lives.
“So we should just take the point and move on and if we’d kicked the ball up the park and pushed up they won’t have scored like they did, it was just a bit of naivety.”
Peterhead have finished seventh in League One and completed their campaign with three games in six days.
McInally believes that may also have been a factor in not managing to take something from the clash with Dumbarton.
He added: “We played against a team that were really fired up and after a poor first 20 minutes we competed with them and ended up playing some decent stuff.
“We got ahead and lost a goal from a corner and that gave them a bit of momentum and they threw everyone forward.
“We should just have taken the point and we need to learn from that because we don’t draw enough games, it’s usually a win or a loss.
“The other thing is you’re making substitutions you wouldn’t normally make because the boys have played Thursday, Saturday, Tuesday.
“Jason Brown had to come off with a hamstring and I don’t think Jason has ever had a hamstring in his time at the club.
“Simon (Ferry) had to come off with a hamstring as well and Niah (Payne) has probably never played as much football as he has in the last few weeks.
“So when you’re into a certain way of playing and having to take important players off it’s difficult.”