I recently got into cycling, but I've noticed that when I clip in my right leg is uncomfortably twisted and my knee hits the frame of the bike when I pedal. When I was very young I broke my leg and unfortunately it did not set completely straight (it set about 10-15 degrees to the outside).
Is there any device or a type of pedal that I could use that will help me pedal a bit easier?
There are a lot of bike fit issues the solutions to which don't come very naturally to a lot of people. Saddle height, fore aft position, handlebar height, and cleat position. This sounds like a cleat position issue. I'd suggest going in to your LBS and paying to get fit on the bike, alternatively if you know some more experienced riders you could have them take a look and make adjustments.
Speedplay pedals have 15 degrees (max) of adjustable rotational "float" which may permit your knee/leg to go into it's natural position when pedaling. If you need a shim under the cleat due to the leg being shorter, those are available from Speedplay as well. If you can find a fitter or sports med type to get you set up properly, that would be the best approach to get you dialed-in.