A couple good options here... And one that's not so good. lol. The bad(opinions vary) one, keep riding as is. My shins are nearly numb now from all the scar tissue so I feel almost nothing from even a hefty smack to the shins. The next option would be shin guards, as suggested already. They make some directed towards bmx riding and others directed more towards downhill and regular mountain biking. My favorite option is taking the step up to clipless pedals wich will keep your feet in place, give you more control, and more power. The pedals will take a little getting used to, but very much worth the cost of admission.