If you have a good heat gun and several good clamps and some hardwood blocks you can clamp on three sides of the bulge then heat the bulge and either tap it down with a flat faced hammer or clamp it flat and let it cool. The hammer will shrink it better but either way it may take a few treatments.
The heat will make it bulge more and hammering it or clamping it flat will force it to shrink, if you use the hammer tap it gently, either way you need enough heat to make it bulge and it needs to cool so you can see how it reacted and how far you have left to go.
Proud Owner of 1956 Vagabond, 1950 Flyer, 1956 Rocket, Co-owner 1952 Flash, 10-1/2 less than VinTin
Finally got the chance to rough in the transom wood for Lisa's boat. The board of mahogany I got was *just big enough to replace the old boards. However, the original outer boards were short of the bottom by about 2". To add those two inches and the two inches to raise the transom height, I'm short on mahogany. Plus the cabinet shop didn't do a great job of planing the board on the ends.