I think its fairly normal for bubs to explore the cot a bit and occasionally hit the side. They really can't do much damage to themselves, it is impossible for them to break their own limbs with their own force. DD has occasionally whacked the side quite hard and not even got a bruise. To start with, she would wake and I would settle her. Within time, she adjusted to the roaming and occasional bump. Now she rarely wakes but if she does, she will roll over and go back to sleep without me doing any-thing.
I suppose my suggestion is to follow the SIDS guidelines as much as you can so bubs isn't getting tangled in any bedding. Let her roam the cot, its really good for them, especially in terms of them self settling as they grow older. Maybe dress bubs more to suit her roaming around and 9 times out of 10, blankets are going to be kicked off. Try not to worry about her hurting herself as she really wont do any damage. Soon enough though, your DD will be crawling, cruising, walking and doing more than enough damage to herself for you to worry about - lol.
Best of luck, it is a stressful time for poor old mum !!!
DD is 3yr 8 months - DS is 6 months