Adding a physics body to a drawn line - ios

Question

I am working on an iOS app with sprite kit where I draw a line in the following way:
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch* touch = [touches anyObject];
CGPoint positionInScene = [touch locationInNode:self];
pathToDraw = CGPathCreateMutable();
CGPathMoveToPoint(pathToDraw, NULL, positionInScene.x, positionInScene.y);
lineNode = [SKShapeNode node];
lineNode.path = pathToDraw;
lineNode.strokeColor = [SKColor blackColor];
lineNode.lineWidth = 5.0f;
[self addChild:lineNode];
}
- (void)touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event
{
UITouch* touch = [touches anyObject];
CGPoint positionInScene = [touch locationInNode:self];
CGPathAddLineToPoint(pathToDraw, NULL, positionInScene.x, positionInScene.y);
lineNode.path = pathToDraw;
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
CGPathRelease(pathToDraw);
}
This is working exactly how I want it to, but I am not sure where to begin with my next step.
I want to create a physics body for the line that I have just drawn.
I would preferable to this in the touchesEnded method.
How can I add a physics body to the line regardless of its width?
My best guess is to track all the points, then do some math to figure out a path along the edge of the line, then add the physics body.
Is there a better way to do this before I dive into my approach?