it just looks like something broke the cell walls on the stem, which often happens with super cropping or a strong wind like defreak says.. when this happens, you get thick knot looking area on the stem where it has repaired itself.. not a big deal usually..
The other guys are most likely right, but do you have any insects that cause galls in your area? If you're taking off any branches with one on it you may want to cut it open, see what's there. It's probably just scar tissue from being bent, but it might be interesting.