Repair roof flashing that is tucked under gutter rather than over it
I wouldn't want to un-nail the bottom row of shingles because the second row could easily be damaged and now you'd have a roof leak. Bending the flashing might work but if you bend it too much, you'll never straighten it back right. Removing the gutter, or removing enough fasteners to slip the gutter under the flashing would be the best, do it right, option.... and wait until it warms up a bit.