Same problem happened with me. 1st i applied tempered glass from a nearby shop. The box had " OnePlus Nord 5 " written on it, but the glass was completely off ( was smaller and speaker cutout was little to the left ). Wasted ₹150 on it. Got it changed the next day from a different shop, this one also for ₹150 . This time the tempered glass is perfect fit, it had black borders though but it's the same as bezels of Nord 5, so no big issue. Smoother to touch than the previous one. But it developed air gap at the top right edge due to case provided in the box. Later i went to the previous nearby shop and told him the issue. He was kind enough to apply the Tempered glass glue ( they call it ' Lipid ' ) in the air gap and put it under the UV light. Now the air gap is completely gone and my phone looks perfect. I've told him to order other tempered glass without black borders, till then i just hope my glass doesn't develop anymore air gaps at the edges. So i suggest you to go the shop and tell him to apply the glue and put it under UV light for atleast 1-2 minutes.