You should avoid stairs as well as you may trip, tumble down them, and dislocate a shoulder.
Joking aside, of course you should continue if you miss it. In the scheme of things a dislocated shoulder is far from the end of the world in the vast majority of cases. I'm 43 and just started last year.
I'm assuming you wear a helmet. Your head isn't the only place you can protect. They sell all sorts of armor to help cushion the blow, most seem to be inspired by motorcross. It really doesn't take a whole lot to greatly reduce the impact. I wouldn't let not having it stop you, but it'll boost your confidence and get you back out and give you some peace of mind.