Work on the other hand. Pick a medium you're comfortable with, then work with your non-dominant hand – if you usually favour your right hand then only use your left and vice-versa.
Deciding on the medium was easy, as sketching with a pen has to be my favorite. I looked up some images online to base this drawing on... and can't believe how well it turned out. The shading's a bit off, and it took about four times longer than it would have if drawn with my right hand, but here is the result!