Gums bleeding after teeth whitening! Is this permanent damage? (Photo)

Recently i got polanight custom fitted teeth whitening trays from my dentist. One night i accidentally put to much of the gel in and my gum burnt like hell and turned white, however i did keep them on for two hours. I had no problems after this until a couple of days later when i ate an apple, it caused that part of my gums to bleed, and it has been bleeding everytime i brush my teeth and hurting ever since! Any advise of what to put on my gums, and is this permanent damage ?? thank you!