This is a common mistake that I’ve made myself, as it only requires a moment of inattention to damage the TPU coating with a hot iron. In most cases it only leaves a small mark on the fabric that doesn’t affect it’s performance, but if the iron is left in contact with the TPU long enough, it can make a hole.
The best way to patch a hole of any size is with a scrap of heat sealable fabric heat sealed over top of it. Color matched scraps are included in the kits for practice and patches.
If you get a tear or puncture in the field, you can use repair tape or Seam Grip or Aquaseal.
For more info on this topic, check out the Punctures, Leaks & Repairs page.
Cheers!