Good Morning! The good news is that you obviously don't have neuropathy! I have pulled twigs, stones, small bits of metal, rocks, rubber, small toy chips, pins and glass out of the soles of feet. Unfortunately, the "owners" of these items had no idea due to his or her neuropathy. Your goals are to reduce the risk of infection and protect this area. An x-ray won't help because it won't pick up the glass, but are you sure that it is a glass splinter? There will also be a hesitancy of the doctor to start probing and cutting because that can make a wound bigger, and maybe the splinter is already out?? Could the pain that you have be the result of inflammation and trauma?
Use what Davebugg suggested for a protective dressing.
To reduce your risk of infection, apply an antimicrobial dressing. I don't know where you are, but the easiest thing would probably be an antibiotic cream for a couple of weeks, (for this acute wound). If your wound ends up as chronic (which I'm sure it won't), switch to iodine or PM me and I can give you other choices and suggestions. Once your wound is closed and you are walking, continue to protect this area with a simple bandage because your wound will still be healing. A lot of remodelling goes on in each skin layer and under the skin and walking is friction and shear on your feet, so trauma can still occur. Oh, and if you're still having some problems with your foot before you leave, you might want to get a prescription for antibiotics filled before your walk "just in case". Insurance may not cover a pre-existing condition. On that cheerful note Buen Camino! It will all be well!