But you really should wear a windbreaker or a long-sleeve with this kind of thing:
McDavid HexPad ForeArm Shivers-Black 651 | GoBros.com
They are for football and they are excellent, and very lightweight, and unlike the soccer shins, they are designed for your forearms. I had your problem, and I wore one of these on one arm under a long-sleeve black shirt, and you couldn't tell a thing. I got nicked, not really drilled, on the same bruise, and I didn't feel it. These things are great.
And if you go to that site right now, they have a lot of deals on compression wear and injury prevention stuff.