Question
While securing a 6" x 6" piece of treated lumber for a landscape border I think I nailed a 12" spike into a large oak or hickory tree root.  I'm estimating it entered about 3 inches in depth.
Should I pull it out and medicate, if there is such or should I let it be.

All the trees measure a miminum of 35 ft tall some as large as 90 ft.

Thanks.  

Answer
Let it be. You would do much more damage to the root system by tring to "medicate" it then the spike will do. The root will more than likely heal itself or the worst that individual root may die--if so this will be a long process and the tree will have compensated for the lost of the root by the time the root dise. Again let it be!