Gosh, that sounds like a nasty fall you had, I hope you are alright now!
I know how you feel because I experienced a simular thing a few years ago.
Have you lost confidence in being around horses as well as riding them, or are you just nervous about riding them?
If you are afraid of being around horses, then why not ask your riding yard if you could help out for a day, and they will probably pair you up with someone who can help you out, and you'll probably really enjoy the day. This could also help your riding because you might bond with a particular pony and you will learn different horses' temperaments.
If you are nervous of riding, then don't be afraid to go back to basics. For instance, don't feel silly about asking your instructor for a lesson on a lead rein. Do this for a few weeks to get used to riding again and remember, you're going to be a lot safer in the school than on a hack (I'm assuming that your fall was on a hack but I don't know!). Ask for steady and reliable horses and try different ones each week. If you find a particular horse that you feel safe on and that you like, then you can ask for this each week. Riding a variety of horses is ideal, but obviously you need to feel safe so if there is one horse that does that for you, then you should ask to ride this one until you're more confident.
When you are riding, you are bound to be nervous. I know it's really hard but try to relax in the saddle and smile. Singing or humming is great for relaxing your body, and this will rub off on your horse. It's going to be tricky at first, so if you feel yourself getting nervous during your ride then explain how you feel to your instructor and maybe ask if you could just halt for a few minutes to relax.
As a rule, never let anybody pressure you into doing things you are not comfortable with. Doing things at your own pace is the only way to gain confidence. If it takes you a few years to canter comfortably then that is fine, don't let anyone force you to do it sooner than you want.
Another rule is not to suffer alone. Talk to a friend, a member of the family or your riding instructor about how you feel, and they will give you tips and make you feel a lot better, trust me. If you don't feel comfortable doing that, then talk to people on here!
Finally, if you book a lesson but then feel like you don't want to go, then be determined. Make it goal to make yourself go for that first lesson. You might find that after that first one, you really missed riding and can't wait to go back, or you might feel that you need longer to mentally recover. Don't dwell in the past, what happened has happened, it was just unlucky that it did happen. Don't be afraid to carry on, and never give up!
I know this message is really long, but I hope it helps, and I hope that you start riding again soon!
P.S. Remember, riding is a fun activity that we do for pleasure, not another chore ;-) Good luck x