I asked the lawyer same question today about the same issue with me. In my case the salary difference is 5 K, He said that should be okay as far as the compnay who has hired you gives you the letter on USCIS RFE that they will pay you whatever salary was mentioned on the Labor Cert.
But if you search forums using keywords such as "salary labor" you will get in detailed information about it. Murthy website also mentiones that the salary should be >= labor cert salary but there are many approvals where salary was < labor salary. This answer has mixed views, ask your attorny!