Highway to the danger zone

Dealing with a crawling baby who is desperately trying to walk has turned our lives into a daily casualty unit.
The laws of gravity insist that what goes up must come down. Ergo, baby who pulls himself up on everything = he falls down a lot. And hits his head on the way down.
Every day Ari has new bruises, scratches and bumps. He woke up from a sleep the other day with a massive red bruise on his forearm. We have NO idea how that one happened but we suspect Ari's done a few rounds with his cot in his sleep and come off second best.
Which brings up another safety related question...when can you put those cot bumper thingies on to prevent such bumping injuries?
The tough thing about being a parent is that for every small fear about injury (cot bruises), there's an even greater fear (cot bumpers = SIDS fears).