1. Heat sealing repair: If the balloon is only slightly damaged at the sealing, it can be heated and resealed with a small heat sealing bag sealer or heat sealing machine.

2. Balloon glue: If the damaged seal is large or cannot be repaired by heat sealing, a special glue suitable for balloons can be used to repair it. Apply a small amount of glue to the damaged seal, press the seal tightly and wait for the glue to dry.

3. Replace the seal: If the damage is serious and beyond repair or a better solution is desired, consider replacing the seal of the balloon.