If you can't play the gig properly, hire a substitute.
If you think you'll be able to "limp by," ask yourself whether your injury will adversely effect the audience's experience or the credibility or professionalism of your band; if the answer is yes, a professional would hire a subsitute for the gig, rather than allow a sub-optimal performance to take place.
You'll heal faster if you take care of yourself. Be good to yourself - you deserve it!
