You’ll have to fire it
You’ll have to fire it longer/hotter than what you would normally full fuse to allow the bubbles to rise and smooth out. Basically, fire it and watch it. Once it’s smooth, skip to anneal.
It’s easier to avoid than repair. Do a little googling on a “bubble squeeze”. I generally heat at a conservative rate to 1100, hold 30, then advanced 50/hr to 1250, hold an hour, then heat to full fuse. The slow advanced to 1250 and the hold there allows the middle to drop without the edges sealing first, so air is pushed out.
Jester’s Baubles Fused Glass Designs