knees & hangnail?

Today it is raining and thus the knees are aching. But the real problem is that I managed to bruise the same knee that has a torn ACL, but just under that knee. I did this somehow while riding my bike yesterday afternoon. Now, I was looking down and noticing that the front tire was pretty low in air, which from what I've been told is not a great idea if you'd like to stay upright and tight on the bicycle. And while I was looking down, I lost my balance for just a moment and began to fall, but I successfully regained my stability, but to the chagrin of my baby knee. Damn! So now, just about ever step is accompanied by a sharp pain shooting from the bottom of the knee, or my accurately the top of the tibia. The ol interweb tells me that this is probably a form of shin splints, which means I'll have to "lay off" the legs for a while, thus leading to atrophy and eventually death, caused by slothiness. Once again, I've found a real pain and a really good way to die from it. What's next? A hangnail?