Can I suggest before proceeding with junction boxes that you turn the power of and investigate whether the cores are damaged. I think I see a shadow of black and red on the left cable but as has already been mentioned it doesn't look as if the damage is much more than superficial from this distance.Yeah, I'm leaning towards a safe repair for my own peace of mind. Any other suggestions to the MF JB approach?
If the inner insulation is not damaged a repair with heatshrink may be all it requires.