removing excess stain from a weathered board

I have an old wood panel The previous owner stained the back of the panel. When I rub a cloth or my hand across the back of the panel my hand or the rag is covered with very dark brown stain. I want to remove the excess stain so when I hang it on the wall the stain is not transferred to the painted wall. What is the best way to dry and rub out the excess stain? Thanks