Do as many others have done- find a stout tree with two trunks close together. Using a long straight-edge, find where the bend is and mark it with a grease pencil, or other visible marking.
Now, insert the barrel between the two trunks, make sure your barrel mark is aligned correctly, and apply a bit of pressure in the opposite direction from the bend, and give it a little nudge.
Being off 3" at 100 yards is really not much of a bend, so be gentle with your correction.
Re-align your sights to barrel central, and shoot a few times. If you are close, leave it be and move your sights as needed. If you are not close, go visit the forked tree again, use a bit more force. Repeat as needed.
On your sight adjustment, remember FORS: Front Opposite, Rear Same. Works every time.