Leaks are the last thing that one would want to have on an air mattress. But it’s a reality and does happen. I have an air mattress, and I have patched a few leaks. The first and foremost thing, when faced with a leak, is to remove the sheets and get the bed to a place where it is easier to maneuver.
Once done, inflate the mattress and check the valve. Most often, it is the primary source of the leak. If the valve is okay, submerge your mattress in water (check for manufacturer instructions) and you can spot the leak. Once detected, use a patch kit, available in local hardware stores, to seal it. The patch kit consists of glue, sandpaper, and patches.
Deflate the mattress, once the leak is detected, use sandpaper to increase the size a bit, cut a piece of the patch (usually bigger than the hole), and apply it to the mattress. Press down the piece for a minute or two. Later on, place a heavy object on the patch and let it dry for 3 to 4 hours. Inflate the mattress afterward and check whether the patch holds and if there are any more leaks.
I hope this was helpful.