I’ve been having some on/off pain on my left big toe. Now the nail bed seems to be turning slightly yellow, only after I started putting hydrogen pero?

Ingrown toenail? That you are putting peroxide on the nail indicates that the pain is there. If the nail is pinching the tissue on either side, it could be getting "ingrown" and/or infected. See a podiatrist, foot and ankle orthopedist or family doctor.