What Causes Nail To Be Not Attached Properly To Nail Bed?

3 years ago a very large can of beans fell on my big toe, second & third toe at an angle, second toe was fractured, big toe nail was bruised at angle front top outside to just below center inside. Relieved pressure with a hot needle. Nail then lifted to where the bruise ended, 9 months later. I cut nail off to that point. It finally started to grow about 1 year later, but continues to not be attached to nail bed. I keep it trimmed so as not to bump it, that really hurts. Although the attachment to nail bed is a little higher, but not much. Why won't it attach/grow properly? It has been 4 years! Not 3 as put at beginning. I am 56 yo female, a little overweight, but active.