Do you mean it's holding you back from applying, or it might hold up you being hired? If you are thinking of not applying because you have never worked on a register before, don't worry about it. You can use a computer...you can use a register. Most places have to train how to use their register anyway because they all have different codes and different way to imput items (either scanning or manually imputing them) but it's definitely not hard to learn. And most employers know they will have to train new employees to use their registers. Believe me, it's no big deal.
If you already applied to Walgreen's and would prefer that job, calling them would be fine. Ask for the manager, and say that you turned in an application and just want to make sure he/she got it. Better yet would be to go and see them in person. Did you turn the application in to the manager or an employee?
Good luck in the job hunt. It's never easy, but hopefully you will find a job you like and pays well. Keep us posted!