Your lender should be able to challenge the appraisal and have FHA send out a new appraiser, for an additional fee of course. That is provided the comps justify the price and your lender has the experience and expertise to know how to do it. Not all do. I had a similar situation in the last 6 months and my lender was able to get it fixed within a week, much to everyone's relief as my clients had already paid quite a bit of money for upgrades on a new home.
Much luck with this.
Barbara S Richie, SFR, SRES, REALTOR
"Experience that counts! The expertise to make it happen!"
Encore Realty Group