If you review the purchase agreement that you signed then you should have a contingency in place for the appraisal. If this contingency is in place and you are still within the contingency period then you are okay. If your home does not appraise at purchase price here are some of your options.
You can renegotiate the purchase price with the seller based on the appraised price.
You can ask for the seller to pay for a second appraisal to see what that comes in at. Remember you will need to make sure that the second appraiser is approved by your lender. Also even with a second appraisal you need to make sure your lender will be okay with that second appraisal. The lender may not be or may even want yet another appraisal after that. This is the main wild card here.
Alternately you can bail out and if you are still within the contingency period you can get your deposit back.
