I have no one to blame but myself. I'm a novice installer! Fortunately the gap is in a closet, so no one's going to be looking. I am curious if anyone has ever filled a gap with wood filler such as the Color Rite? I'm installing Brazilian Cherry so there is a lot of grain and color variation. The gap is probably 1/8 to 3/16" wide at one end. I won't bother telling you how I screwed up, but I couldn't be troubled to tear it out and start over. No ones going to know but me.

If it is site finished flooring you could probably fill it with some wood filler. If it is prefinished, I would probably leave it as is.